Important Questions Class 10 Science Chapter 3

Important Questions Class 10 Science Chapter 3 Metals and Nonmetals

The third chapter of CBSE Class 10 Science is about metals and non-metals. The chapter explains different types of metals, nonmetals, occurrences, their differences, reactions with other elements, symbols, and positions on the periodic table.

Extramarks is one of the best online study platforms for lakhs of students. Our experienced science teachers have created multiple study guides to help students with their studies and ongoing exam preparation. One of the important features of our study solutions is our question bank of important questions for Class 10 Science Chapter 3. Apart from the solutions to important questions, students will find many other study materials such as NCERT solutions, CBSE revision notes, past year question papers, etc.

Our question and answer study guide for Important Questions Class 10 Science Chapter 3 is a valuable resource for students preparing for the Science board exam. CBSE Class 10 Science is an important subject and will be a deciding factor in the next year, so students must prepare thoroughly. To support students excelling in science  Extramarks’ experts have prepared a guide to important questions and their step-by-step solutions. These questions will help students understand the questions expected on the board exam. It will give students good practise, and they will be able to face the board exam with confidence and get excellent grades.

The questions in our Chapter 3 Class 10 Science Important Questions are carefully designed and chosen to ensure that they cover all the topics from the chapter. So, by revising questions from the Extramarks question bank, students will be able to cover the entire CBSE and NCERT Class 10 Science syllabus. The questions follow the CBSE exam pattern after analysing the past years’ question paper patterns, marks distribution   and the types of questions asked.

Each answer in our question set of Important Questions for Class 10 Science Chapter 3 is prepared by experienced science teachers. It provides a step-by-step explanation that covers important concepts from the chapter. By going through these solutions, students will be able to fully revise the chapter and further strengthen their understanding of the subject.

We recommend students register on the Extramarks website and get full access to our question and answer set of Class 10 Science Chapter 3 Important Questions. These important questions are important in their Class 10 Science board exam since they follow NCERT exam guidelines and are aligned with the Class 10 Science syllabus. So it prepares students to revise all the main concepts with great clarity so that they can answer any advanced-level questions easily in board exams and come out with flying colours.

CBSE Class 10 Science Important Questions 2022-23

CBSE Class 10 Science Important Questions are also available for the following chapters:

Important Questions Class 10 Science Chapter 3: With Solutions

At Extramarks, we highlight important concepts and questions from each chapter which help students with their studies right before their board examinations. Solving the Important Questions Class 10 Science Chapter 3 will familiarise the students with the questions asked in final examinations. Science is an important subject which requires deep conceptual understanding, so cramming answers won’t help, especially in the higher  classes.

Many 10th grade students have found our Important Questions Class 10 Science Chapter 3 Metals And Nonmetals study aid very helpful. Students are suggested to go through these important questions during revision. The best time to practice these questions is at least two months before the board examination. Solving these selected questions will help in getting excellent  marks in Science papers.

Given below are some of the questions and their answers from our list of questionnaires of Important Questions Class 10 Science Chapter 3.

Question1: Metal always found in a free state is:

• Gold
• Silver
• Copper
• Sodium

Answer 1: (a) Gold

Explanation: Gold (noble metal) occurs in the native state. The metals at the bottom of the activity series, like gold, platinum and silver, are the least reactive. They are often found in the free state because this metal does not react with air.

Question 2: The earthy impurities associated with minerals used in metallurgy are called

• Slag
• Flux
• Gangue
• Ore

Answer 2: The correct option is (c) Gangue

Explanation: The waste materials accompanied with minerals while extracting are called Gangue particles. It is an earthly impurity with no electrical or magnetic properties. Gangue is not valued in the market and is a rock, sand, or soil waste. It is present along with minerals in the ore deposit from which the metal is extracted. Therefore the correct option is c.

Question 3: Malachite is an ore of:

• Iron
• Copper
• Mercury
• Zinc

Answer 3: the correct answer is (b) Copper

Explanation:  Malachite is a copper carbonate hydroxide mineral with the formula Cu2CO3(OH)2. It is an ore of copper. Therefore the correct option is b.

Question 4: A process employed for the concentration of sulphide ore is

• Froth floatation
• Roasting
• Electrolysis
• Bessemerisation

Answer 4: The correct option is (a) Froth floatation

Explanation: The froth floatation method is based on the concentration of sulphide ores. This technique is based on the wetting properties of the ore and gangue particles. Sulphide ore is grounded and is dropped in a mixture of water and pine oil (oil and water create a suspension). In this tank, the compressed air is blown through the agitator, which is rotated. Due to agitation, the gangue particles settle down, and sulphide ore floats upside down. These two are separated in different tanks, and the sulphide ore is sent for further processing. The oil and gangue preferably wet the sulphide ores with water. Thus this method is suitable for the concentration of the sulphide ore, and the correct option is a.

Question 5: The setting of Plaster of Paris takes place due to

• Oxidation
• Reduction
• Dehydration
• Hydration

Answer 5: The correct option is (d) Hydration

Explanation: the setting of plaster of paris is due to the formation of calcium hydrate. Hydration of POP is the hydration reaction which is the reverse of the reaction of gypsum dehydration. Plaster of paris, when turned into  a thin paste with water, quickly sets to a hard mass. A slight expansion occurs during this process because it is exothermic, which means that heat has evolved.

The reaction involves is:

2CaSO4.H2O + H2O →  CaSO4.2H2O

Therefore the correct option is d

That is, the setting of the plaster of paris involves the hydration to yield another hydrate.

Question 6: Most abundant metal on the surface of the earth

• Iron
• Aluminium
• Calcium
• Sodium

Answer 6: The correct option is (b) Aluminium

Explanation: The most abundant metal on earth is aluminium metal. Aluminium is the third most abundant element in the earth’s crust, making up 8 percent of it by parts per million. It is a very lightweight and silvery-white metal. It is a good conductor of electricity and heat. Therefore the correct option is b.

Question 7: Zone refining is used for the

• The concentration of an ore
• Reduction of metal oxide
• Purification of metal
• Purification of an ore

Answer 7: The correct option is (c) Purification of metal

Explanation: The zone refining process is special. William Pfann invented this method. The other techniques similar to the zone refining process for a particular use are distillation, liquidation, electrolytic refining, and chromatographic methods.

The zone refining process is used for the purification of metals.

Metals are purified through this process to a very high degree. The other name for zone refining is called fractional crystallisation. Through this process, ultra-pure samples of metals like germanium, silicon, boron, and gallium are obtained. A Zone Refining (Fractional Crystallisation) method is employed to get metal of very high purity, i.e. ultra pure samples of Ge, Si, B, Ga, In. This method is based on more soluble impurities than the pure metal. So the correct option is c.

Question 8: In addition to iron, stainless steel contains:

• Nickel and Chromium
• Copper and Tin
• Aluminium and Magnesium
• Carbon and Magnesium

Answer 8: The correct option is (a) Nickel and Chromium

Explanation: In addition to iron, carbon modern stainless steel may also contain nickel, niobium, molybdenum, chromium and titanium. Nickel, niobium, molybdenum, & chromium improve the corrosion resistance of stainless steel. Hence, stainless steel, in addition to iron-nickel and chromium, imparts tensile strength to the alloy.

Question 9: The lustre of a metal is due to

• Its high density
• It’s high polishing
• It’s chemical inertness
• Presence of free electrons.

Answer 9: The correct option is (d) the presence of free electrons.

Explanation: Metals are lustrous because of the free electrons present in them. The light falling on these electrons is reflected. Thus, the metal surface appears shiny or polished.

Question 10:Chemically rust is

• Hydrated ferrous oxide
• Hydrated ferric oxide
• Only ferric oxide
• None of these

Answer 10: The correct option is (b) Hydrated ferric oxide

Explanation: Rust is a reddish-brown oxide developed by the interaction of iron and oxygen molecules in the presence of water or atmospheric moisture. The formation of rust is called a chemical process. Various forms of rust can be distinguished both visually and by spectroscopy. Rust consists of hydrated iron (III) oxides Fe2O3.nH2O.

It occurs in moist air and water. As we already discussed in a previous class, rust requires three chemicals to form: iron, oxygen, and water.

4Fe + 3O2 + 2H2O → 2Fe2O3.H2O

Hydrated iron(III) oxide is also called hydrated ferric oxide because here, the oxidation state of iron is +3. Due to the rusting process, the iron degrades and becomes useless and weak. So, the correct answer is option b.

Question 11: Heating pyrites to remove sulphur is called

1. Smelting
2. Calcination
3. Liquation
4. Roasting

Answer 11: The correct option is (d) Roasting

Explanation: In roasting, the ore is heated in a regular supply of air in a furnace at a temperature below the melting point of the metal. Some of the reactions involving sulphide ores are:

2ZnS + 3O2 → 2ZnO + 2SO2

2PbS + 3O2 → 2PbO + 2SO2

Hence, the correct answer option is d.

Question 12: Which of the following oxides is amphoteric?

• Na2O
• MgO
• CaO
• Al2O3

Answer 12: The correct option is (d) Al2O3

Explanation: An amphoteric oxide is an oxide that can act as either an acid or base in a reaction to form salt and water. Al2O3 reacts with acid as well as a base. Hence, it is amphoteric. Hence, option A is correct.

Question 13: Give an example of a metal which

(i) can be easily cut with a knife.

(ii) is a liquid at room temperature.

Answer13:

(i) Sodium

(ii) Mercury

Explanation: i)Sodium metal is soft enough to be cut with a knife. Lithium and potassium are soft metals that can be easily cut with a knife.

ii)Mercury is liquid at room temperature. Lithium, sodium, & potassium are all soft metals easily cut with a scalpel or knife. Silver is a good conductor of both heat and electricity among metals.

Question 14: Reverse of the following chemical reaction is not possible-

Zn (s) + CuSO4 (aqueous) → ZnSO4 (aq) + Cu (s)

Justify this statement with reason(s).

Answer 14: ZnSO4 (aq) + Cu (s) → X (no reaction)

Because Cu is less reactive than Zn in the activity series, less reactive metal (Cu) does not displace more reactive metal (Zn) from its salt solution. Thus, this reaction is not possible.

Question 15: Why is copper used to make hot water tanks, whereas steel is not?

Answer 15: Copper is a good conductor of heat compared to steel. Therefore, hot water tanks are made of copper.

Explanation: Copper, rather than steel or an alloy of iron, is used to make hot water tanks because copper does not react with either water or steam, while iron reacts with steam to corrode the tank. Copper is unaffected by cold water, hot water, or steam, whereas iron is influenced by steam.

Question 16: Why does metal not release H2 gas on reacting with dilute nitric acid?

Answer 16: As nitric acid acts as a strong oxidising agent and oxidises the released H2 gas to H2O, it is reduced to either of these gases – N2O, NO2 or NO.

Explanation: Hydrogen gas is not evolved if a metal interacts with a nitric acid solution. It is because HNO3 is a  very strong oxidising agent. It oxidises the H2 produced in water and reduces itself to any of the nitrogen oxides (N2O, NO, NO2). But magnesium (Mg) & manganese (Mn) react with very dilute nitric acid solution HNO3 to evolve H2 gas.

Question 17: Why is metal sodium kept immersed in kerosene oil?

Answer 17: Sodium is highly reactive. It interacts vigorously with both air and water and burns. So it is immersed in kerosene oil to avoid contact with air and water.

Explanation: Sodium is kept in Kerosene because this metal is very reactive, and its interactions with water are extremely exothermic. It reacts vigorously with oxygen and water. It can react with water vapour and oxygen in the air and produce a lot of heat. Sodium does not react with Kerosene. Therefore, it is stored or kept in Kerosene to avoid this violent reaction.

Question 18: Complete the following equation with balancing: 

(i) Al + HCl →

(ii) Mg + HNO3 →

Answer 18:The balanced chemical reactions are shown below-

1. i)     2Al      +            6HCl(aq)                      →       2AlCl3 (aq)   +     3H2(g)↑

Aluminium      Hydrochloric acid            Aluminium chloride   Hydrogen

(ii)       Mg(s)     +           2 HNO3 (aq)         →    Mg(NO3)2 (aq)  + H2↑

Magnesium      nitric acid(very dilute)          Magnesium nitrate    Hydrogen

Question 19: (a) Complete and balance the following chemical equations-

(i) Al2O3 + HCl →

(ii) K2O + H2O(l) →

(iii) Fe + H2O(l) →

(b) An element ‘X’ replaces iron from the aqueous solution of iron sulphate. List your observations when the element ‘X’ is treated with the aqueous solutions of copper sulphate, zinc sulphate and silver nitrate solution. Depending on the statements, arrange X, Zn, Cu and Ag in increasing order of their reactivities.

Answer19:The balanced chemical reactions are-

(a) (i) Al2O3 + 6HCl(l) → 2AlCl3 + 3H2O

(ii) K2O + H2O(l) → 2KOH

(iii) 3Fe + 4H2O(l) → Fe3O4 + 4H2

(b) As X replaces iron from its salt solution, X is more reactive than iron. It will also replace copper from copper sulphate solution and silver from silver nitrate as both are less reactive than iron. As zinc is more reactive than iron, X can be more or less reactive than zinc. Then the order of their reactivities can be

Ag < Cu < Fe < Zn < X or Ag < Cu < Fe < X < Zn.

Explanation: b) An element X displaces iron from the aqueous solution of iron sulphate. A more reactive metal replaces a less reactive metal from its salt solution. It means element X is more reactive than iron.

X + FeSO4(aq)        →             XSO4(aq) + Fe

Pale green colour               (colourless)

The pale green colour of iron sulphate will fade away slowly when element X is treated with the aqueous solutions of CuSO4.

X   + CuSO4(aq)   →   XSO4(aq) +  Cu

(blue)                 (colourless)

Copper is less reactive than iron; iron is less reactive than X. It means copper is less reactive than X.

The blue colour of copper sulphate will fade away slowly. The deposits of metal X  will be seen on the copper strip. X can displace silver from its silver nitrate solution as silver is less reactive than copper. The increasing order of reactivities of these metals X, Zn, Cu, and Ag is as:

X + ZnSO4(aq)     →   XSO4(aq) +  Zn

X + AgNO3(aq)→   XNO3(aq) +  Ag

(colourless)          (colourless)

X displaces iron, which is more reactive than copper and silver; that is why  X is a highly reactive metal of all given metals.

Ag< Cu< Zn< X

Question 20:  What are alloys?

Answer 20: An alloy is a homogeneous mixture of two or some more metals, or metal & a nonmetal. It is synthesised by first melting the primary metal and then dissolving the different elements in it in definite proportions. It is then cooled at  room temperature.

Examples are Brass, an alloy of copper and zinc (Cu and Zn), and bronze, an alloy of copper and tin (Cu and Sn).

Question 21: Write equations for the reactions of

(i) iron with steam

(ii) calcium and potassium with water

Answer 21: (i) Iron reacts with steam to form a magnetic oxide of Fe with the liberation of H2 gas.

3Fe(s) + 4H2O(gas) → Fe3O4(s) + 4H2(g)

(ii) As Calcium metal interacts with water to form calcium hydroxide and hydrogen gas.

Ca(s) + 2H2O(l) → Ca(OH)2(aqueous) + H2(g)

Potassium interacts with cold water violently  with the evolution of H2 gas, which catches fire. .

2K(s) + 2H2O(l) → 2KOH(aq) + 2H2(g)

Explanation: i) Iron reacts with steam and forms iron oxide. The reaction is shown below:

1. ii) Calcium and potassium react with water to give their respective hydroxides. The reactions are shown above.

Question 22: Why do ionic compounds have high melting points?

Answer 22: Ionic compounds are the ones that have both positive and negative charges. Thus there will be a strong force of attraction between them. It consumes a lot of heat to break this force of attraction; therefore, ionic compounds have high melting points.

Explanation: The ionic compounds have a very strong electrostatic force of attraction. To overcome these forces, very high energy is needed. Thus, the melting point of ionic compounds is generally quite high.

Question 23:Explain the meanings of malleable and ductile.

Answer 23: Metals that can be beaten to sheets are malleable. Metals that can be drawn into thin wires are said to be ductile.

Explanation: Malleable: Substances that can be beaten into thin sheets are called malleable. For example, most metals are malleable.

Ductile: Substances which can be drawn into thin wires are called ductile. For example, most metals are ductile; refer to Important Questions Class 10 Science Chapter 3.

Question 24: What chemical process is used for obtaining a metal from its oxide?

Answer 24: The reduction method obtains metal from its oxide. Ex.- Zinc oxide is reduced to metallic zinc metal by heating with carbon.

ZnO + C → Zn(s) + CO

Example: Lead oxide is reduced to lead by heating with carbon

PbO +C → Pb + CO

Explanation: The chemical process for obtaining a metal from its oxide is reduction. This method reduces the metal oxide solution by using suitable reducing agents such as carbon or highly reactive metals to replace the metals from their oxides.

For ex., zinc oxide is reduced to metallic zinc by heating with carbon.

ZnO(s) + C(s) + heat → Zn(s) + CO(g)

Manganese dioxide is reduced to manganese by treating it with aluminium powder. In this case, aluminium displaces manganese from its oxide.

3MnO2(s) + 4Al (solid) → 3Mn(l) + 2Al2O3(s) + heat

Oxides of more reactive metals are reduced by electrolysis.

Question 25: Which of the following methods is suitable for preventing an iron frying pan from rusting?

• Applying grease
• Applying paint
• Applying a coat of zinc
• All of the above

Answer 25: The correct option is (c) Applying a coat  of zinc

It will be the most suitable method to prevent it. Though applying grease and paint prevents iron from rusting, we cannot use these methods on a frying pan; hence applying a coat of zinc is the most appropriate method to prevent an iron pan from rusting.

Explanation: We can also apply grease and paint to prevent iron from rusting. However, in the case of an iron frying pan, grease and paint cannot be used because when the pan is heated and washed again and again, the coating of grease and paint won’t last long enough.

Question 26:  Which of the following pairs will give displacement reactions?

(i) NaCl solution and copper metal

(ii) MgCl2 solution and aluminium metal

(iii) FeSO4 solution and silver metal

(iv) AgNO3 solution and copper metal

Answer 26: The correct option is (iv), i.e. AgNO3 solution and copper is the right answer. Copper replaces the silver cations (reducing them to the elemental metal) in the process of copper itself being oxidised to Copper II cations (Cu2+) and going into solution. Hence silver metal precipitates out, and a copper II nitrate solution will remain.

Cu(s) + 2AgNO3 (aqueo) → Cu(NO3)2 (aq) + 2Ag (s)

Explanation: The correct answer is silver nitrate solution and copper metal. The solution metal is more interactive than the given metal in all other options.

For, e.g . in (b) MgCl2 solution and aluminium metal, Mg metal is more reactive than aluminium. Thus, chemical reactions will not take place.

Question 27: Which metals do not corrode easily?

Answer 27: Metals placed at the bottom of activity series like silver, gold, and platinum do not corrode easily.

Explanation: The least reactive metals, such as gold, don’t rust easily, whereas highly reactive elements are corroded easily. That is why these metals (highly reactive) are given gold plating to protect them from corrosion—examples: gold, platinum, silver and copper.

Question 28: An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

(a) Calcium

(b) Carbon

(c) Silicon

(d) Iron

Answer 28: A Correct answer is an option (a) that is calcium..

Calcium interacts with oxygen to give calcium oxide solution. Calcium oxide solution is soluble in water to give Calcium Hydroxide.

Carbon forms carbon-oxide with oxygen, that is, gas; thus, option b is incorrect.

Silicon interacts with oxygen and forms silicon dioxide. This is insoluble in water. So option c is not correct.

Iron reacts with oxygen and forms Iron dioxides. This is insoluble in water. So option d is not correct.

Explanation: The correct element is calcium. Calcium oxide solution is soluble in water and has a high melting point.

Question 29: You are given a hammer, a battery, a bulb, wires & a switch.

(a) How could you utilise them to distinguish between samples of metals and nonmetals?

(b) Assess these tests’ usefulness in distinguishing metals and nonmetals.

Answer 29: a) Metals are malleable and can be easily drawn into sheets by hitting with a hammer. On the other hand, if we beat nonmetals, they break down and cannot be drawn into sheets as they are non-malleable. Metals are good conductors of electricity; hence they make a bulb when you connect metals with a battery, wire and bulb. Similarly, If nonmetals are bad conductors of electricity, chances are they will fail to light up the bulb on connecting with wire and battery.

1. b) These experiments can help demonstrate metals and nonmetals’ malleability and electric conductivity.

Explanation: a) Metals are naturally malleable. We can beat the given sample with the help of a hammer. If it turns into thin sheets, it is metal; otherwise, it is a nonmetal.

Metals carry electricity. We use a battery, a lamp, wires, and a switch to create a circuit. If the bulb glows, the sample is metallic due to liberated electrons. When the bulb does not light  up, the sample is non-metallic.

1. b) These tests represent the physical properties of metals and nonmetals. We can easily distinguish between them based on their physical characteristics.

Question 30: Food cans are coated with tin & not with zinc because

(a) Zinc is costlier than tin Sn.

(b) Zinc has a maximum melting point than tin Sn.

(c) Zinc is more reactive than tin.

(d) Zinc is less reactive than tin.

Answer 30: The correct option is c. Food cans are coated with tin, not zinc because zinc is more reactive than electropositive tin.

Explanation: Zinc is more interactive than tin. So zinc can react with food items and make food unhealthy to consume. So the correct option is c.

Question 31: State two ways to prevent the rusting of iron.

Answer 31: i) Iron can be prevented from rusting by coating the surface of the iron with rust-proof paints

1. ii) Oil/grease on the surface of iron objects will prevent the iron surface from getting in contact with air consisting of moisture.

Explanation: The process of degrading metals in the presence of air and water is known as rusting. Two ways in which rusting can be prevented are shown below:

i)Oiling, greasing, or Painting: By applying oil, grease, or paint, the surface becomes waterproof, and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented.

1. ii) Galvanisation: In this process, iron articles are coated with a layer of zinc metal, which prevents the iron from coming in contact with oxygen and moisture. Hence, rusting is prevented.

Question 32: Give reasons-

(a) Platinum, gold & silver are used to make jewellery.

(b) Sodium(Na), potassium(K) & lithium(Li) are stored under oil.

(c) Aluminium is a highly interactive metal, yet it is utilised to make utensils for cooking.

(d) Carbonate & sulphide ores are generally converted into oxides during the process of extraction

Answer 32:

(a) Platinum, gold & silver are used to make jewellery, for these metals are less reactive; hence they are not affected by air, water or most chemicals. These metals have a lot of lustre properties. They are malleable and ductile and also have high corrosion resistance in nature.

(b) Sodium, potassium & lithium readily interact with water to produce a lot of heat. In conclusion, hydrogen evolved in the reaction, resulting in fire. On exposure to water, they interact with the  moisture (water droplets) in the atmosphere. These metals are stored under an oil tumbler to prevent contact with water.

(c) Aluminium forms on its surface a non-reactive surface of aluminium oxide. Such coating prevents different compounds from reacting to aluminium. So aluminium is being utilised to develop utensils for the cooking purpose..

(d) Reducing metal oxide converted into free metal is easy. Generally, because it is easier to obtain metals directly from their oxides than from their carbonates or sulphides, the carbonate & sulphide ores are first transformed into oxides to get the metals.

Explanation: a) Platinum, gold, and silver are used to make jewellery because they are lustrous. Also, these are very less reactive and do not rust easily.

(b) Sodium, potassium, & lithium are very reactive metals and react vigorously with air and water. Therefore, they are immersed in kerosene oil to prevent their contact with air and moisture.

(c) Although aluminium is highly reactive, it is resistant to corrosion. It is because aluminium reacts with oxygen in the air to form a thin aluminium oxide layer. This oxide layer is very stable & prevents further interaction of aluminium with oxygen. Also, it is light in weight & the best conductor of heat. Thus, it is used to make cooking utensils.

(d) Carbonate and sulphide ores are generally converted into oxides during extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulphides.

Question 33: Define the following terms :

(i) Minerals

(ii) Ores and

(iii) Gangue

Answer 33:

(i) Minerals:  The elements or compounds occurring naturally in the earth’s crust are minerals.

(ii) Ores: Minerals from which metal can be extracted profitably and easily are called ores.

(iii) Gangue: Impurities such as soil and sand, which are present in the minerals, are called gangue.

Explanation: i) Minerals are compounds (also known as elements) found naturally in the earth’s crust. Ex., Alums, K2SO4.Al2(SO4), 3.24H2O, etc.

3. ii) Ores are minerals from that metal that can be extracted. Ex: Bauxite Al2O3.2H2O is the ore of aluminium, copper pyrite CuFeS2. All minerals are not considered ores, but all ores are also considered minerals.

iii) Ores mined from the earth’s crust are naturally contaminated with sand and rocky materials. There are impurities present in the ore that is known as gangue.

Question 34: What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer 34:  Amphoteric oxides are the one which reacts with both acids and bases to form salt and water—examples:  Lead oxide – PbO and Aluminium oxide – Al2O3.

Explanation: Amphoteric oxides are those oxides of metals that behave in both an acidic & basic manner. These oxides interact with acids and bases to produce salt and water as the major products. E.g. Aluminium oxide (Al2O3  and Zinc oxide (ZnO).

Question 35: In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer 35: In the electrolytic refining of metal called ‘M’, an impure and thick block of metal M. is considered an anode; a thin strip or wire of pure metal M is used as a cathode. A perfect salt solution of metal M is regarded as the electrolyte.

Explanation: In the electrolytic refining of a metal M:

Anode → Impure metal M

Cathode → Thin strip of pure metal M

Electrolyte → Solution of salt of the metal M

Question 36: You must have seen tarnished copper vessels cleaned with lemon or tamarind juice. Explain why these sour or citrus substances are effective in cleaning the vessels.

Answer 36: Tarnished copper vessels are cleaned with lemon or tamarind because this acidic substance contains acids that dissolve the coating of copper oxide or basic copper carbonate on the surface of tarnished copper vessels. It makes them shine red-brown again. Thus they are very effective in cleaning tarnished copper vessels.

Explanation: Copper reacts with moist carbon dioxide in the air to form copper carbonate(CuCO3.Cu(OH)2). As a result, the copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid in the lemon or tamarind neutralises the base copper carbonate and dissolves the layer. That is why tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.

Question 37: A man went from door to door posing as a goldsmith person. He promised to turn back  the glitter of old & dull gold ornaments. An unsuspecting lady gave him a set of gold bangles that he dipped in a particular solution. The bangles sparkled, i.e. new, but their weight was reduced drastically. The lady was sad, but after a futile argument, the man beat a hasty retreat. May you play the detective to find out the nature of the solution he had used?

Answer 37: Goldsmith used the solution called Aqua regia, which is called royal water in Latin. It is the combination of concentrated Hydrochloric acid & concentrated nitric acid in the ratio of 3:1. Aqua regia solution can dissolve noble metals like gold and platinum. They lose weight when the upper layer of dull gold ornaments is dissolved.

Explanation: The man uses Aqua Regia, three parts of HCL and 1 part of HNO3 solution. Gold is the least reactive metal, but when we put it in aqua regia, the uppermost layer gets dissolved in the solution, and the inner layer comes out, which weighs less than before but is more glittery..

Question 38:  Differentiate between metal and nonmetal based on their chemical properties.

Answer 38:The major differences between metals and nonmetals are given below:-

Question 39: Name two metals which will displace hydrogen from dilute acids and two metals which will not.

Answer 39: Zinc (Zn) and Magnesium (Mg) are the metals that will displace hydrogen from dilute acids as they are very reactive. Gold (Au) & Silver (Ag) are the metals which will not replace hydrogen from dilute acids as these metals are less reactive.

Explanation: More reactive metals will displace hydrogen from its dilute acids. For example, Iron and Zinc.

Fe+2HCl → FeCl2+H2

Zn+2HCl→ZnCl2+H2

Least reactive metals will not displace hydrogen from their dilute acids—for example, copper and silver.

Cu+HCl→ No Reaction

Ag+HCl→ No Reaction

Question 40: Give an example of a metal which

(i) Is a liquid at room temperature?

(ii) Can it be easily cut with a knife?

(iii) Is the best conductor of heat?

(iv) Is it a poor conductor of heat?

Answer 40:

(i) Mercury is a metal which is liquid at room temperature.

(ii) Sodium and potassium are metals that can be cut with a knife.

(iii) Silver is a good conductor of heat.

(iv) Mercury and lead are poor conductors of heat.

Question 41: (i) Write the electron-dot structures for sodium & oxygen.

(ii) Show the formation of sodium oxide Na2O and MgO by the transfer of electrons.

(iii)What are the ions +nt in these compounds?

Answer 41 : (i) Sodium:

        Na͘

Oxygen-

• Ọׂ࣭̇͘     

(ii) Formation of Magnesium oxide-

When magnesium interacts with oxygen, the magnesium atom transfers its two outermost electrons to an oxygen atom. By losing two electrons, the magnesium atoms create a magnesium ion (Mg2+); by gaining two electrons, the oxygen atom forms an oxide ion (O2-).

Mg:  +  ·Ọׂ࣭̇͘  → MgO

Formation of Sodium oxide:

Two sodium atoms transfer their two outermost electrons to an oxygen atom. The two sodium atoms create sodium ions (2Na+) by losing two electrons. & by gaining 2 electrons, the oxygen atom forms an oxide ion (O2-).

2Na.       +    ·Ọׂ࣭̇͘        →   Na2O

(iii) The ions present in sodium oxide compounds (Na2O) are sodium ions (2Na+) and oxide ions (O2-).

The ions present in Magnesium oxide compounds (MgO) are magnesium ions Mg2+ and oxide ions (O2-).

Explanation: i) Sodium, oxygen and magnesium atomic numbers are 11, 8 and 12. The electron dot structures are below:

Sodium (2,8,1) =Nax

Oxygen (2,6) =

Magnesium (2,8,2) = Mgxx

ii)Both of the compounds will form an ionic bond.

iii)Na2O, the ions 2 Na+ and O2- and in MgO are Mg2+  and O2-

Question 42: Pratyush took a sulphur powder on a spatula & heated it. He collected the evolved gas by inverting a test tube over it, as given in the figure provided in the book.

(a) What will be the reaction of gas –

(i) dry litmus paper?

(ii) moisture litmus paper?

(b) Write a balanced equation for the chemical reaction taking place-

Answer 42: a) When the sulphur powder is burnt in the air, sulphur-di-oxide is formed.

(i) Sulphur-di-oxide doesn’t have any effect on dry litmus paper.

(ii) Sulphur-di-oxide turns the moist litmus paper from blue to red as contact of SO2 with water turns to sulphurous acid.

(b) S(s) + O2(g) → SO2(g)

SO2(g) + H2O(l) → H2SO3 (aq)

Explanation: (a) (i) There will be no action on dry litmus paper.

(ii) Since the gas is sulphur dioxide (SO2), it turns moist blue litmus paper to red because sulphur dioxide reacts with moisture to form sulphurous acid.

(b) S(s) + O2(g) → SO2(g)        Sulphur dioxide

SO2(g) + H2O(l) → H2SO3 (aq)    Sulphurous acid

Question 43: The ability of metals to be drawn into thin wires is known as

(a) ductility

(b) malleability

(c) sonority

(d) conductivity

Answer 43: The correct answer is (a) ductility

Explanation:

• Ductility is the physical property of metals that can be drawn into thin wire.
• Malleability is a physical property of metals that defines their ability to be hammered, pressed or rolled into thin sheets without breaking.
• Sonority is the ability of a metal to be sonorous, which means it can make or produce a deep, ringing sound.
• Conductivity is the ability of a metal to conduct electricity. So the correct answer is option a.

Question 44: Which of the following metals does not react with cold or hot water?

(a) Na

(b) Ca

(c) Mg

(d) Fe

Answer 44: A correct answer is an option (d) Fe

Explanation-

Sodium & calcium interact vigorously with water, & magnesium reacts with hot water to form Magnesium Oxide. Iron does not react with cold hot water but with steam.

Question 45: Aluminium is used for making cooking utensils. Which of the aluminium is responsible for the same?

(i) Good thermal conductivity or good heat conduction

(ii) Good conduction of electricity

(iii) Ductility

(iv) High melting point

(a) (i) & (ii)

(b) (i) & (iii)

(c) (ii) and (iii)

(d) (i) and (iv)

Answer 45: The Correct option is (d) – (i) and (iv)

Explanation: As we know, electrical conductivity and ductility have no relevance for a cooking utensil, and it does not enhance cooking. Aluminium is used  for making cooking utensils because it is a good conductor of heat and has a melting point of about 660 °C. So, the aluminium vessel would not melt while cooking when on  the stove. Thus, the correct answer is option (d).

Question 46: Which of the following properties is generally not shown by metals?

(a) Electrical conduction

(b) Sonorous

(c) Dullness

(d) Ductility

Answer  46: The correct option is (c) Dullness

Explanation: Out of all the given options, dullness is the only property not shown by any metal, as the metals are lustrous. Thus, the correct answer is option (c).

Question 47:  Which of the following oxide(s) of iron would be obtained on the prolonged reaction of iron with steam?

(a) FeO

(b) Fe2O3

(c) Fe3O4

(d) Fe2O3 and Fe3O4

Answer 47: The correct option is (c) Fe3O4

Explanation: Iron does not react with cold or hot water, but steam is passed over a red hot iron; it reacts to form iron (II, III) oxide and hydrogen gas.

3Fe(s) + 4H2O(gas) → Fe3O4 (s)    +  4H2 (g)               at 1062 –  1072k

Thus, the correct answer is option (c)

Question 48: What happens when calcium is treated with water?

(i) It does not react with water

(ii) It reacts violently with water

(iii) It interacts less violently with a water molecule

(iv) Bubbles of hydrogen H2 gas formed stick to the surface of calcium Ca

(a) (i) & (iv)

(b) (ii) and (iii)

(c) (i) and (ii)

(d) (iii) and (iv)

Answer 48: The correct answer is options (d) (iii) and (iv). Calcium interacts slowly with water. When a piece of calcium is dropped into a non-reactive container containing water after some time, bubbles of hydrogen gas are seen stuck to the surface of the metal.

Explanation- Calcium reacts vigorously with water and forms hydrogen, making calcium float. Thus, the correct answer is option (d).

Ca + 2H2O  → Ca(OH)2 + H2

Question 49: Which of the given properties is not generally exhibited by ionic compounds?

(a) Solubility in water

(b) Electrical conductivity in solid-state

(c) High melting and boiling points

(d) Electrical conductivity in a molten state

Answer 49: A correct answer is an option (b) Electrical conductivity in solid-state

Explanation- In an ionic compound, free ions are not available in the solid-state hence solid ionic compounds cannot conduct electricity. Thus, the correct answer is option (b).

Question 50:  Generally, metals interact with acids to give salt & hydrogen gas. Which of the given acids does not give hydrogen gas on reacting with metals (except Mn & Mg)?

(a) H2SO4

(b) HCl

(c) HNO3

(d) All of these

Answer 50: A correct answer is an option  (c) HNO3

Nitric acid is a powerful oxidising agent. It interacts with the metal to form water.

Explanation: Out of the given options, only nitric acid, when reacting with metals, does not provide hydrogen gas; instead, nitric acid is a very strong oxidising agent and oxidises the hydrogen gas formed in water, and thus hydrogen gas is not evolved. Therefore, the correct answer is option (c).

Question 51: The composition of aqua-regia is

(a) Dil.HCl: Conc. HNO3 3: 1

(b) Conc.HCl: Dil. HNO3 3: 1

(c) Conc.HCl: Conc.HNO3 3: 1

(d) Dil.HCl: Dil.HNO3 3: 1

Answer 51: A correct answer is option (c) Conc.HCl: Conc.HNO3 3: 1

Explanation: Aqua-regia is a mixture of concentrated hydrochloric acid and nitric acid in a molar ratio of 3: 1. Thus, the correct answer is option (c).

Question 52: Which of the following are not ionic compounds?

(i) KCl

(ii) HCl

(iii) CCl4

(iv) NaCl

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iii)

Answer 52:The correct answer is an option (b) (ii) & (iii)

Explanation: HCl & CCl4 are covalent compounds; hence they cannot be ionic. It has covalent bonding within its atoms. Thus, the correct answer is option (b).

Question 53: Which of the following metals exist in their native state in nature?

• Cu
• Au
• Zn
• Ag

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (ii) and (iv)

(d) (iii) and (iv)

Answer 53: The correct answer is an option (c) (ii) and (iv)

Gold and silver are non-reactive metals because they are non-reactive. They exist in their native state.

Explanation: Silver and gold are noble metals, and in nature, they exist in their free state and not in any combined state as ore. Thus, the correct answer is option (c).

Question 54: Metals are refined by using different methods. Which of the following metals are purified by electrolytic refining?

(i) Au

(ii) Cu

(iii) Na

(iv) K

(a) (i) & (ii)

(b) (i) & (iii)

(c) (ii) and (iii)

(d) (iii) and (iv)

Answer 54: The  correct answer is an option (a) (i) and (ii)

Explanation: Among the given metals, sodium (Na) and potassium (K) are highly reactive metals extracted by the electrolytic reduction of their molten chloride salts. Copper (Cu) & gold (Au) are extracted by electrolytic refining. Thus, the correct answer is option (a).

Question 55: Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of

(a) Gallium

(b) Aluminium

(c) Zinc

(d) Silver

Answer 55: The correct answer is an option (c) Zinc

Galvanization is a method of applying a layer of zinc on iron by using electrolysis.

Explanation: Galvanisation is a method to protect iron articles from rusting. In this process, a thin coating of a more reactive metal like zinc is coated on top of the iron article to be protected. Therefore, the correct answer is option (c).

Question 56: Silver articles become black on prolonged exposure to air. That is due to the formation of

(a) Ag3N

(b) Ag2O

(c) Ag2 S

(d) Ag2S and Ag3N

Answer 56: A correct answer is an option (c) Ag2S

Explanation: Silver metal reacts with sulphur present in the atmosphere to form Ag2S.  It is responsible for the black colouration of silver articles.

4Ag(s) +2H2S(g)  + O2(gas) →  2Ag2S(s) + 2H2O(l)

Therefore the correct answer is an option(c), referring to important questions in Class 10 Science Chapter 3.

Question 57: Stainless steel is a very useful material for our life. In stainless steel, iron is mixed with

(a) Ni and Cr

(b) Cu and Cr

(c) Ni and Cu

(d) Cu and Au

Answer 57: A correct answer is option (a) Ni and Cr

Generally, Stainless steel is an alloy of Iron, Nicker & chromium. This alloy makes the metal strong, durable & corrosion-resistant.

Explanation- Stainless steel is an alloy of iron made by mixing different metals like about 11% of chromium, nickel, molybdenum and niobium etc. and carbon with a maximum concentration of about 1.2%. Therefore, the correct answer is option (a).

Question 58: Generally, metals are solid. Which one of the given metals is found in a liquid state at room temperature?

(a) Na

(b) Fe

(c) Cr

(d) Hg

Answer 58: A correct answer is option (d) Hg because mercury is the metal present in the liquid state at room temperature.

Explanation: Mercury is a metal that has a melting point of -38.83 °C. Hence, at room temperature, it exists in the liquid state. So, the correct answer is option (d).

Question 59: If copper is kept open in the air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of

(a) CuSO4

(b) CuCO3

(c) Cu(NO3)2

(d) CuO

Answer 59: A correct answer is an option (b) CuCO3

Metals are usually reactive. When left exposed to air, the pure copper metal starts reacting with atmospheric gases like carbon dioxide and water vapour. That leads to the formation of copper carbonate and others. Copper carbonate makes the shiny copper metal dull and greenish.

Explanation: Copper metal, kept open in the air, slowly undergoes the process of corrosion to develop a characteristic blue-green coating on top of the metal surface. The corrosion of copper metal in air forms in several steps-

4Cu(s) + O2(g) → 2Cu2O(s), red colour

Cu2O(s) + O2(s) → 2CuO(s), black colour

2CuO(s) + CO2(g) + H2O(l) → CuCO3(s) + Cu(OH)2(s), green colour

So, the correct answer is option (b).

Question 60: Which of the following metals are obtained by electrolysis of their chlorides in a molten state?

(i) Na

(ii) Ca

(iii) Fe

(iv) Cu

(a) (i) and (iv)

(b) (iii) and (iv)

(c) (i) and (iii)

(d) (i) and (ii)

Answer 60: The correct answer is an option (d) (i) and (ii). Sodium and calcium are at the top of the reactivity series

Explanation: Sodium and calcium are the metals obtained from their chloride ores by electrolysis in the molten state. Therefore, the correct answer is option (d).

Question 61: Generally, nonmetals are not lustrous. Which of the following nonmetals is lustrous?

(a) Sulphur

(b) Oxygen

(c) Nitrogen

(d) Iodine

Answer 61: The correct answer is option (d) Iodine

Explanation: Iodine, in nature, exists in its molecular crystalline form, and due to this, iodine has a lustrous character. Therefore, the correct answer is option (d).

Question 62: Which of the following four metals would be displaced from the solution of its salts by the other three metals?

(a) Mg

(b) Ag

(c) Zn

(d) Cu

Answer 62: The correct answer is option (b) Ag. Because silver Ag is a non-reactive metal, it can be replaced easily.

Explanation: Out of the given options, silver metal is the least reactive metal, and so it can be displaced by the other metals from its salt. So, the correct answer is option (b).

Question 63: 2 mL each of concentrated hydrochloric acid HCl, nitric acid HNO3 and a combination of concentrated HCl and concentrated nitric acid HNO3 in the ratio of 3: 1 were taken in test tubes labelled as A, B & C. A few pieces of metal were put in each test tube. No change occurred in test tubes A & B, but the metal dissolved in test tube C. The metal could be

(a) Al

(b) Au

(c) Cu

(d) Pt

Answer 63: The correct answer is an option (b) Au

The answer is gold because solution C is a mixture of Concentrated HCl and Concentrated HNO3, called aqua regia. Aqua Regia dissolves gold.

Explanation: A mixture of concentrated HCl and HNO3 in the 3: 1 molar ratio is termed aqua regia. It is a yellowish-orange fuming liquid which can dissolve gold.

Thus, the correct answer is option (b).

Question 64:  Alloys are homogeneous metal mixtures with a metal or nonmetal. Which among the following alloys contain nonmetal as one of its constituents?

(a) Brass

(b) Bronze

(c) Amalgam

(d) Steel

Answer 64: The correct answer is option (d) Steel

Steel is an alloy of carbon and iron, whereas carbon is a nonmetal.

Explanation: Steel is an iron alloy with other metals like nickel, chromium, niobium and carbon. Therefore, the correct answer is option (d).

Question 65: Which among the given statements is not correct for magnesium Mg metal-

(a) It burns in oxygen gas with a dazzling white flame

(b) It interacts with cold water to form magnesium oxide & evolves hydrogen gas

(c) It interacts with warm water to form magnesium hydroxide and evolves hydrogen gas

(d) It interacts with steam to form magnesium hydroxide and evolves hydrogen gas

Answer 65: A correct answer is an option (b). It interacts with cold water to form magnesium oxide & evolves hydrogen gas.

Magnesium interacts with cold water to form magnesium oxide and evolves hydrogen gas is a wrong statement because Magnesium Hydroxide is created, not Magnesium oxide.

Explanation: Magnesium does not interact with cold water. It only interacts with hot water or steam to form magnesium hydroxide and hydrogen gas. So, the correct answer is option (b).

Question 66: Generally, nonmetals are not conductors of electricity. Which of the given is the best conductor of electricity?

(a) Diamond

(b) Graphite

(c) Sulphur

(d) Fullerene

Answer 66: The answer is (b) Graphite

Explanation: Out of all the following options, only graphite is a good conductor of electricity due to the presence of free electrons. Therefore, the correct answer is option (b).

Question 67:Electrical wires have a coating of insulating material. The material generally used is

(a) Sulphur

(b) Graphite

(c) PVC

(d) All can be used

Answer 67: The correct answer is option (c) PVC

Sulphur is brittle; hence it can be used, and graphite is a good conductor of electricity and cannot be used as an insulator.

Explanation: Polyvinyl chloride is a synthetic plastic polymer which is a bad conductor of electricity and is thus used as an insulating coating material for metallic wires. Therefore, the correct answer is option (c).

Question 68: Iqbal treated a lustrous, divalent element M with sodium hydroxide NaOH solution. He notices the formation of bubbles in a reaction mixture. He made the same observations if this element was treated with hydrochloric acid HCl. Suggest how he can identify the produced gas. Write chemical equations for both reactions.

Answer 68: A lighted matchstick should be brought near the gas to identify the produced gas. If a match stick burns with a “pop” sound, it indicates the evolution of Hydrogen gas.

M (s)+ 2NaOH(aq) + heat  → Na2MO2+ H2

Reaction with HCl

M (s)+ 2HCl(aq) →MCl2  +  H2

Explanation: The lustrous divalent element M can be an amphoteric metal like Zn, Sn or Pb. When reacting with sodium hydroxide NaOH, it forms sodium zincate & hydrogen gas. If zinc is treated with hydrochloric acid, it comprises zinc chloride and hydrogen gas, which is why Iqbal made the same observation.

Zn (s)+ 2NaOH(aq) + heat  → Na2ZnO2+ H2(g)

Reaction with HCl

Zn(s)+ 2HCl(aq) → ZnCl2  (aq)+  H2

To test the hydrogen gas produced in the chemical reaction, if a glowing splint is brought near the gas produced, it will burn with a pop sound.

Question 69: Compound X and aluminium are used to join railway tracks. (a) Identify the compound X (b) Name the reaction (c) Write down its reaction.

Answer 69:

1. a) Answer is Fe2O3
2. b) The involved reaction is a thermite reaction which is also called aluminothermy
3. c) Fe2O3(s) + 2Al(s)        →       Al2O3 (s) + 2Fe(s) + Heat

Ferric oxide  Aluminium     Aluminium Iron Oxide.

Question 70: What are the constituents of solder alloy? Which property of solder makes it fitting for welding electrical wires?

Answer 70: Solder alloy is made of lead & aluminium metal. Its low melting point makes it perfect for welding electrical wires.

Question 71: A nonmetal A which is the largest constituent of air, when heated with H2 in a 1:3 ratio in the presence of a catalyst (Fe), gives a gas B. On heating with O2, it provides an oxide with C. If this oxide is passed into the water in the presence of air, it gives an acid D which shows as a strong oxidising agent-

(a) Identify A, B, C & D

(b) To which group of modern periodic tables does this nonmetal belong?

Answer 71: a) Nonmetal “A” is nitrogen because it is the largest constituent of air, constituting around 78% of the gases. B is Ammonia, C is Nitrogen-di-oxide & D is Nitric acid solution.

If heated with H2 in a 1:3 ratio in the presence of a catalyst (Fe) the following reaction takes place.

N2  + 3H2 (g)→ 2NH3

Heating Nitrogen gas with O2 gives nitrogen-di-oxide

N2(g) +2O2(g) →2NO2(g)

When nitrogen dioxide is passed into the water in the presence of air, it gives Nitric acid

4NO2 (g)+ 2H2O(l) + O2(g)→ 4HNO3(aq)

b)Nitrogen belongs to group 15 of the modern periodic table

Question 72: Explain the following points-

(a) Reactivity of Aluminium metal decreases if it is dipped in nitric acid HNO3

(b) Carbon cannot reduce the oxides of sodium Na or Mg 

(c) NaCl is not a  good conductor of electricity in the solid state, whereas it does conduct electricity in an aqueous solution as well as in a molten state

(d) Iron articles are galvanised.

(e) Metals like sodium potassium, calcium Na, K, Ca, and Mg are never found in their free state in nature.

Answer 72:

1. a) Reactivity of Aluminium metal decreases if it is dipped in nitric acid solution HNO3 because HNO3 is a strong oxidising agent. Here, a layer of aluminium oxide gets collected because this reactivity of aluminium metal gets reduced.

(b) Carbon cannot reduce the oxides of sodium or magnesium Na or Mg because these are highly reactive metals. Na & Mg have a higher affinity to oxygen than carbon. Therefore carbon fails to reduce the oxides of Na and Mg metal.

(c) NaCl is not a  good conductor of electricity in the solid state. In contrast, it conducts electricity in an aqueous and molten state because NaCl is an ionic compound. Ionic compounds cannot conduct electricity in a solid state but can conduct electricity in an aqueous and molten state.

1. d) Iron readily interacts with atmospheric oxygen and forms rust. To avoid rusting of iron, it is galvanised.
2. e) Metals like Na, K, Ca & Mg are highly reactive metals. They can form compounds with almost all elements. Due to this, they are not found in their native form in nature.

Question 73: An element A burns with golden flame in the air. It interacts with different element B, atomic number 17, to give a  final product, C. So An aqueous solution of product C on electrolysis provides a compound with D and liberates hydrogen gas.

Identify A, B, C & D. Also, write down the equations for the reactions involved.

Answer 73:

Element A is Sodium metal because it will burn with a golden flame in the air.

Element B is a Chlorine atom, for its atomic number is 17.

Product C is Sodium Chloride

2Na +Cl2 →2NaCl

Product D is Sodium hydroxide

2NaCl+ 2H2O→ 2NaOH+ Cl2+H2

Question 74: Of the three metals, X, Y and Z. X react with cold water, Y with hot water & Z with steam only. Identify X, Y & Z and also arrange them in order of increasing reactivity.

Answer 74:

X reacts with cold water.

Hence, the x element should be sodium or potassium metal.

2Na + 2H₂O → 2NaOH + H₂

Y reacts with hot water; hence, y could be “Magnesium or Calcium.”

Mg + H₂O →  Mg(OH)₂ + H₂

Z reacts with steam only. Hence, it is iron or zinc

4Fe + 6H₂O → 2Fe₂O₃ +  6H₂

Arranging in this metal ascending order (increasing order of reactivity)

Fe < Mg < Ca

Question 75: Two ores, A & B, were taken. On heating, ore A gives CO2, and ore B provides SO2 molecules. What process will you take to convert them into metals?

Answer 75: Ore A gives CO2 on heating; so it is a carbonate ore

The process involved in the Extraction of ore A

1. i) Calcination-

Ore is heated in a very low supply of air to obtain a metal oxide

ACO3 → AO + CO2(g)

ii)Reduction-

If the metal oxide is reduced with coke to form metal atoms.

AO + C → A(s) + CO(g)

So Ore B is a sulphide ore.

The process involved in the extraction of element B is-

1. a) Roasting-

Ore is heated in the presence of the atmosphere to obtain a metal oxide

2BS + 3O2(g) → 2BO + 2SO2

1. b) Reduction-

The metal oxide is reduced to metal atom by carbon

BO + C→ B(s) + CO

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