Important Questions for CBSE Class 11 Chemistry Chapter 14 – Environmental Chemistry

Students should ensure that their Class 11 Chemistry concepts are clear else they would face challenges in Class 12 Chemistry. Chapter 14 of Class 11 Chemistry is about ‘Environmental Chemistry’. The chapter discusses Environmental Chemistry and its various important aspects such as the study of the origin, movement, reactions, outcomes, and fates of chemical species in the environment. You will understand various reasons for global warming, the greenhouse effect and acid rain. The chapter will also cover topics of ozone layer depletion and its effects, water pollution, air pollution, and international standards of drinking water.

It is crucial that all of the topics of the chapter are fully understood in order for the students to score well in exams. Students, along with the NCERT textbook, can rely on the study materials available on Extramarks’ website. We are the trusted source of information for many students from grades 1 to 12. Our comprehensive study resources have already helped lakhs of students across the country.

Our team understands the importance of regularly solving questions to have a better grip on the chapter. As a result, we have included numerous sets of questions from various references and sources in our question bank of Important Questions Class 11 Chemistry Chapter 14 to help students understand each topic covered in the chapter.

Important Questions Class 11 Chemistry Chapter 14 includes questions taken from the NCERT textbook, NCERT Exemplar, and numerous other reference materials. A group of Chemistry subject experts selects the questions through a lot of research and after analysing a lot of past years’ question papers. Students are assured that they are studying the correct material as all our solutions are based on the latest NCERT guidelines and CBSE syllabus.

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Environmental Chemistry Class 11 Important Questions and Answers

The Important Questions Class 11 Chemistry Chapter 14 include various questions as well as their detailed solutions. The questions given in the question bank will cover important theories related to the chapter as well as significant themes including strategies for control of environmental pollution and also the importance of green chemistry in day-to-day life. Students will be able to efficiently understand the environmental issues and their effects by making use of this material in an efficient manner.

Given below are a few selected questions and answers from our Class 11 Chemistry Chapter 14 important questions.

Question 1: Dinitrogen and dioxygen are the main constituents of air but these do not react with each other to form oxides of nitrogen because _________.

(i) the reaction is endothermic and requires a very high temperature.

(ii) the reaction can be initiated only in presence of a catalyst.

(iii) oxides of nitrogen are unstable.

(iv) N2 and O2 are unreactive.

Answer 1: (i)

Explanation: Due to the presence of a triple bond and the extremely high dissociation energy of N2, these gases do not react with one another at room temperature.

Question 2: Which of the following statements about photochemical smog is wrong?

(i) It has a high concentration of oxidising agents.

(ii) It has a low concentration of the oxidising agent.

(iii) It can be controlled by controlling the release of NO2, hydrocarbons, ozone etc.

(iv) Plantation of some plants like pinus helps in controlling photochemical

smog.

Answer 2: (ii)

Explanation: Photochemical smog contains a lot of oxidants as it contains formaldehyde, nitric oxide, peroxyacetyl nitrate, and acrolein. Photochemical smog has many negative health effects.

Question 3: Which of the following statements is wrong?

(i) Ozone is not responsible for the greenhouse effect.

(ii) Ozone can oxidise sulphur dioxide present in the atmosphere to sulphur

trioxide.

(iii) Ozone hole is thinning of the ozone layer present in the stratosphere.

(iv) Ozone is produced in the upper stratosphere by the action of UV rays on

oxygen.

Answer 3: (i)

Explanation: O3 makes up between 8 and 10% of the greenhouse effect. The earth’s surface absorbs about 75% of solar energy, while the remaining 25% is reflected back into space. This heat traps atmospheric gases like CO2, CH4, O3, CFCs, and H2O, increasing the temperature of the atmosphere and contributing to global warming.

Question 4: Which of the following statements is not true about classical smog?

(i) Its main components are produced by the action of sunlight on

emissions of automobiles and factories.

(ii) Produced in a cold and humid climates.

(iii) It contains compounds of reducing nature.

(iv) It contains smoke, fog and sulphur dioxide.

Answer 4: (i)

Explanation: Due to the gases that are generated by factories and automobiles, classic smog develops in cold, humid climates. The classic smog is made up of a mixture of SO2, smoke, and fog.

Question 5: Which of the following gases is not a greenhouse gas?

(i) CO

(ii) O3

(iii) CH4

(iv) H2O vapour

Answer 5: (i)

Explanation: Carbon monoxide (CO) is not considered a direct greenhouse gas, mostly because it does not absorb terrestrial thermal IR energy strongly enough

Question 6: Define Environmental Chemistry.

Answer 6: Environmental Chemistry is the study of chemical and biological processes that take place in the natural environment. It also explores the interaction, origin, effects, and movement of biochemical species on earth.

Question 7: What is the troposphere?

Answer 7: The lowest part of the atmosphere is the troposphere. It is the layer of the atmosphere where people and other animals can be found. It rises to a height of roughly 10 km above sea level.

Question 8: List gases which are responsible for the greenhouse effect.

Answer 8: The main cause of the greenhouse effect is carbon dioxide(CO2). Methane(CH4), nitrous oxide(NO), water vapour(H2O), CFCs, and ozone(O3) are other greenhouse gases.

Question 9: Which disease is caused due to ozone layer depletion?

Answer 9: When the ozone layer in the atmosphere is depleted, the chance of skin cancer among living organisms increases. Through the ozone layer’s gaps, the sun’s UV radiation penetrates the earth and causes ailments to the skin.

Question 10: What is the desired concentration of Fluoride ion (F-) in drinking water?

Answer 10: PHS advises community water systems that add fluoride to their water to reduce the incidence of dental fluorosis to have a fluoride concentration of 0.7 mg/L (parts per million [ppm]).

Question 11: What do you mean by Biochemical Oxygen Demand (BOD)?

Answer 11: Biochemical Oxygen Demand is the volume of oxygen that bacteria need to consume in order to break down the organic material that is present in a specific amount of the water sample. A BOD level of less than 5 ppm indicates that the water is clean, whereas one of 17 ppm indicates that the water is extremely polluted.

Question 12: What is PAN?

Answer 12: Peroxyacetyl nitrate or PAN  is a secondary pollutant that is present in photochemical smog. When heated, it breaks down into peroxy ethanol radicals and nitrogen dioxide gas.

Question 13: What are biodegradable and non-biodegradable pollutants?

Answer 13: Biodegradable pollutants are those that can be broken down by bacteria. It includes waste from fruits and vegetables, cow dung, and other organic materials.

Non-biodegradable pollutants are those that cannot be broken down by microbes. It includes substances like mercury, polythene, DDT, and others.

Question 14: How can domestic waste be used as manure?

Answer 14: The garbage must first be divided into biodegradable and non-biodegradable segments. Food wastes and other materials that can be broken down by bacteria are biodegradable and are disposed of in landfills with the microorganisms that break them down. The final product, Humus, a degraded substance, can be used as manure in crops. The remainder of the garbage, which cannot be decomposed, must be recycled.

Question 15: Why does water cover with excessive algal growth become polluted?

Answer 15: The addition of fertilisers with phosphate increases the growth of algae on the water’s surface, which makes the water unfit for swimming or boating and gives off a foul odour. It also reduces the amount of oxygen in the water, which can be dangerous for aquatic life.

Question 16: What is pneumoconiosis?

Answer 16: A pneumoconiosis is a form of interstitial lung illness brought on by breathing specific kinds of lung-damaging dust particles. Being more likely to be exposed to these clouds of dust at work, pneumoconiosis is considered to be occupational lung disease.

Question 17: Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?

Answer 17: Carbon dioxide (CO2) and carbon monoxide (CO) gases are released when different fuels are burned. While carbon dioxide is naturally non-toxic, carbon monoxide is harmful.

Carbon monoxide is dangerous because it can combine with haemoglobin to produce a more stable complex than the oxygen-haemoglobin complex, carboxyhemoglobin. The blood’s ability to carry oxygen is reduced when carboxyhemoglobin levels are between 3 and 4%. Headaches, poor vision, jitters, and cardiovascular issues are common occurrences. At higher concentrations, it can be more fatal. In normal cases, carbon dioxide is not dangerous but it can prove to be fatal at higher concentrations.

Question 18: The greenhouse effect leads to global warming. Which substances are responsible for the greenhouse effect?

Answer 18: There are many different greenhouse gases, some of which are produced naturally and others that are created by humans. Natural gas called methane is created when vegetation burns, digests, or rots in the absence of oxygen. Large amounts of methane are released into the atmosphere by paddy fields, coal mines, fossil fuels, and decaying waste.

Although nitrous oxide is present in the atmosphere naturally, it is rising daily as a result of human activity.

ACs employ CFCs (Chlorofluorocarbons), which are man-made. Additionally, they produce greenhouse gases.

Question 19: What is the importance of measuring the BOD of a water body?

Answer 19: BOD is a measurement of the amount of organic material in water based on how much oxygen is needed for biological breakdown. Clean water is defined as having a BOD value of less than 5 ppm, whereas severely contaminated water has a BOD value of 17 ppm or above.

Question 20: What do you mean by green chemistry? How will it help decrease environmental pollution?

Answer 20: The goal of green chemistry is to develop and execute chemical products and processes that will limit the use and synthesis of compounds that are harmful to the environment by utilising the chemistry that is already known and understood and its underlying principles.

Environmental pollution results from the emission of several hazardous compounds (particulates, gases, organic wastes, and inorganic wastes). In green chemistry, the reactants that will be used in chemical reactions are selected so that the final products will produce up to 100% of their total yield. This minimises or inhibits the release of chemical contaminants into the environment. Tetrachlorethane and chlorine gas have been substituted with H2O2 in the drying and bleaching of paper due to the efforts of green chemists.

Question 21: What are the harmful effects of oxides of nitrogen in the atmosphere?

Answer 21: The harmful effects of oxides of nitrogen in the atmosphere are as follows:

• High amounts of NO2 injure plants by causing leaf spotting, a reduction in photosynthetic activity, and suppression of vegetative growth.
• In humans, nitric oxide leads to bronchitis and respiratory problems. It results in photochemical haze and acid rain.
• Nitrogen oxide fractures rubber and harms fibres such as nylon, rayon, and cotton.
• They also interact with ozone in the atmosphere, reducing ozone density.

Question 22: Ozone is a toxic gas and is a strong oxidising agent. Even then its presence in the stratosphere is very important. Explain what would happen if ozone from this region is completely removed.

Answer 22: Ozone gas, which makes up the stratosphere, shields us from the sun’s dangerous UV rays (= 225 mm). UV radiation can injure people and result in melanoma, eye cataracts, genetic mutations, and crop devastation. Aquatic creatures and plants may also have a negative impact. The atmospheric release of chlorofluorocarbons (CFCs) is the primary cause of ozone depletion.

So, even though O3 is detrimental to us while it is in the troposphere, it shields us from radiation when it is in the stratosphere.

Question 23: Statues and monuments in India are affected by acid rain. How?

Answer 23: Acid rain is a consequence of a number of human activities that release sulphate and nitrogen oxides into the atmosphere. After being oxidised, these oxides combine with water vapour to create acids.

2SO2(g)   + O2(g)   +  2H2O(l)   →  2H2SO4(aq)

4NO2(g)   +  O2(g)   +  2H2O(l)   →  4HNO3(aq)

Buildings and infrastructures composed of stone and metal suffer are damaged from acid rain. A significant stone utilised in the Taj Mahal and other famous statues and structures in India is limestone.

Limestone responds to acid rain as follows:

CaCO3   +  H2SO4     →  CaSO4   +  H2O   +  CO2

Thus, the monuments become pale and lose their colour and lustre.

Question 24: Ozone is a gas heavier than air. Why does the ozone layer not settle down near the earth?

Answer 24: There is a dynamic equilibrium between the creation and decomposition of ozone because it is a thermodynamically unstable gas and can be broken down into molecular oxygen.

O2(g)   →   O(g)    +     O(g)

O(g)    +   O2(g)   →   O3(g)

Question 25: What are the reactions involved for ozone layer depletion in the atmosphere?

Answer 25: The reactions involved in ozone layer depletion in the atmosphere are:

CFCs are discharged into the atmosphere and combined with other gases before reaching the stratosphere, where  UV light decomposes them.

CF2CL2(g)   →   Cl+(g)     +      CF2Cl(g)

The chlorine-free radical produced in the first steps reacts with the ozone as: 

         Cl–(g)      +     O3(g)    →    ClO– (g)      +    O2(g) 

The chlorine free radical further reacts with atomic oxygen to produce more chlorine free radicals as follows:

ClO– (g)    +  [O]    →     Cl–(g)  +  O2(g)

Question 26: Explain tropospheric pollution in 100 words.

Answer 26: Tropospheric pollution is mostly caused by the presence of unfavourable elements in the atmosphere’s base layer, such as solid or gaseous particles.

The following are the principal pollutants found in the troposphere: 

1. Gaseous Pollutants: These mostly include sulphur (SO2 & SO3), nitrogen, and carbon oxides, hydrogen sulphide(H2S), hydrocarbons, ozone, and other oxidants.
2. Particulate pollutants: The principal components include smog, dust, mist, and fumes.

Burning fossil fuels such as coal and gasoline releases sulphur and nitrogen oxides, which when they come into contact with water make nitric acid (HNO3) and sulphuric acid(H2SO4), respectively, and so cause acid rain.

2SO2   + O2  +  H2O  →  2H2SO4

4NO2   + O2  +2H2O  → 4HNO3

Question 27: Green plants use carbon dioxide for photosynthesis and return oxygen to the atmosphere, even then carbon dioxide is considered to be responsible for the greenhouse effect. Explain why.

Answer 27: CO2 contributes to global warming. Although it is caused by the combustion of fossil fuels, plants take inCO2 for photosynthesis and release oxygen in return, which slows down global warming.

Only found in the troposphere, CO2 makes up 0.03% of the total volume of the atmosphere.

But as we all know, using fossil fuels and deforestation both result in higher CO2 levels, which further adds up to global warming.

Question 28: Some time ago the formation of polar stratospheric clouds was reported over Antarctica. Why were these formed? What happens when such clouds break up by the warmth of sunlight?

Answer 28: Over the South Pole of Antarctica, scientists working there noticed ozone layer depletion or the existence of an ozone hole. It was found that the ozone hole was caused by a certain set of components based on the seasons.

While polar stratospheric clouds build up over Antarctica in the winter, nitrogen dioxide and methane combine with chlorine monoxide and chlorine atoms in the summer to create chlorine sinks that stop ozone depletion.

During the winter, polar stratospheric clouds above Antarctica provide a surface on which hypochlorous acid is formed by the hydrolysis of chlorine nitrate. It also reacts with HCl to produce molecular chlorine.

ClO + NO2 (g) → ClONO2 (g)

Cl (g) + CH4 → CH3 (g) + HCl (g)

ClONO2 (g) + H2O → HOCl (g) + HNO3

ClONO2 (g) + HCl → Cl2 (g) + HNO3 (g)

In the spring, as the sun rises once again, the warmth of the sun penetrates the cloud, protolyzing HOCl and Cl2.

HOCl (g) → OH(g)Cl(g)

Cl2 → 2Cl (g)

The resulting chlorine radicals trigger the chain of ozone depletion.

Question 29: Write down the reactions involved during the formation of photochemical smog.

Answer 29: The interaction of sunlight with hydrocarbons and nitrogen oxides results in photochemical smog. Common elements of photochemical smog include ozone, nitric oxide, acrolein, formaldehyde, and peroxyacetyl nitrate (PAN). The process that causes photochemical smog to occur can be summed up as follows:

The burning of fossil fuels releases nitrogen dioxide and hydrocarbons into the atmosphere. High levels of these pollutants in the air cause them to interact with sunlight in the following ways:

NO2(g)         →             NO(g)    +    O(g)

Nitrogen dioxide           Nitric oxide 

O(g)        +        O2(g)          ↔    O3(g)

O3(g)       +       NO(g)          →    NO2(g)     +       O2(g)

While both NO2 and O3 are oxidising agents, ozone is hazardous by nature. They create formaldehyde, PAN, and acrolein when they interact with the unburned hydrocarbons in the air.

3CH4    +    2O3   →    3CH2=O         +       3H2O

                                     Formaldehyde

Question 30: Explain how does greenhouse effect cause global warming.

Answer 30: The term “greenhouse effect” describes global warming that occurs as a result of the atmosphere absorbing heat that is radiated from Earth into space. Some gases in the atmosphere act like the glass in a greenhouse, letting sunlight enter but preventing the heat from the Earth from escaping into space. Gases including water vapour, carbon dioxide (CO2), methane, nitrous oxides, and chlorofluorocarbons all contribute to the greenhouse effect (CFCs).

Benefits of Solving Important Questions of Environmental Chemistry Class 11

Environmental Chemistry concepts from Class 10 will be largely utilised in Classes 11 and 12. Therefore, in order to have a solid conceptual knowledge of all the concepts covered in the higher classes, it is crucial that the students practise the Chemistry Class 11 Chapter 14 Important Questions diligently. Students will have a thorough practice of the Environmental Chemistry chapter once they have fully solved all questions from our Important Questions Class 11 Chemistry Chapter 14.

The benefits of practising questions from our Chapter 14 Class 11 Chemistry Important Questions are listed below:

• It helps them to evaluate themselves. By solving Important Questions Class 11 Chemistry Chapter 14, students will come to know where they are lagging. They can concentrate more on that particular topic. 
• It improves students’ critical and analytical thinking abilities. It gives students an overall idea of how the questions might appear in their exams and helps them stay prepared. 
• A team of professionals reviews and verifies the questions and answers before providing them to the students. So students can completely rely on our study resources.
• These NCERT important questions will help to build a strong foundation for their CBSE Class 12 board exams. 

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