CBSE Sample Paper 2022-23 Class 12 Solutions

Q1. What type of extrinsic semiconductor crystal is obtained in a pure semiconductor crystal of Si. Draw the energy band diagram of this extrinsic semiconductor so formed.

Q2. Consider two different hydrogen atoms. The electron in each atom is in an excited state. According to the Bohr model, is it possible for the electrons to have different energies but the same orbital angular momentum? Justify your answer.

Q4. Derive an expression for the frequency of radiation emitted when a hydrogen atom de-excites from level n to level (n – 1). Also, show that for large values of n, this frequency equals the classical frequency of revolution of an electron.

Q5. Explain with a proper diagram how an ac signal can be converted into a dc ( pulsating)signal with an output frequency double the input frequency using the PN junction diode. Give its input and output waveforms.

Q6. How long can an electric lamp of 100 W be kept glowing by fusing 2 kg of deuterium?

Q7. Define wavefront. Draw the shape of the refracted wavefront when the plane incident wave undergoes refraction from optically denser to rarer medium. Hence prove Snell’s law of refraction.

The focal length of a convex lens made of glass of refractive index (1.5) is 20 cm. What will be its new focal length when placed in a medium of refractive index 1.25? Is focal length positive or negative? What does it signify? Q11. (a) Name the e.m. waves suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves. (b) If the Earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now? Explain. (c) An e.m. a wave exerts pressure on the surface on which it is incident. Justify.

1. Arrange the following in the increasing order of their property indicated (any 2):

a. Benzoic acid, Phenol, Picric acid, Salicylic acid (aka values).

b. Acetaldehyde, Acetone, Methyl tert butyl ketone (reactivity towards NH2OH).

c. ethanol, ethanoic acid, benzoic acid (boiling point) (1×2=2)

2. Solutions of two electrolytes, ‘ A’ and ‘B’, are diluted. The Λm of ‘B’ increases 1.5 times

while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your

answer. Graphically show the behaviour of ‘A’ and ‘B’. (2)

3. Give reasons to support the answer:

a. Presence of Alpha hydrogen in aldehydes and ketones is essential for aldol condensation.

b. 3 –Hydroxypentan-2-one shows positive Tollens test. (1×2=2)

4. Account for the following:

a. The ammonolysis of chlorobenzene cannot prepare aniline under normal conditions.

b. N-ethylethanamine boils at 329.3K, and butanamine boils at 350.8K, although both are isomeric.

c. Acylation of aniline is carried out in the presence of pyridine. (1×3=3) 

12. Read the passage given below and answer the questions that follow.

 Are there nuclear reactions going on in our bodies?

There are nuclear reactions constantly occurring in our bodies, but there are very few of them compared to chemical reactions, and they do not affect our bodies much. All physical processes that keep a human body running are chemical processes. Nuclear reactions can lead to chemical damage, which the body may notice and try to fix. They eventually transform to a stable form through radioactive decay

a. Why is Carbon -14 radioactive while Carbon -12 is not? (Atomic number of Carbon: 6)

b. Researchers have uncovered the youngest known dinosaur bone, dating around 65 million

years ago. How was the age of this fossil estimated?

c. Which are the two most common radioactive decays in the human body?

d. Suppose an organism has 20 g of Carbon -14 at its time of death. Approximately how much

Carbon -14 remains after 10,320 years? (Given antilog 0.517 = 3.289) 

Write balanced chemical equations for the following:

 (i) Reaction of chlorine with hot and concentrated NaOH.

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 (ii) Sulphur dioxide is passed through an aqueous solution of Fe (III) salt.

10. 0.5 g of KCl was dissolved in 100 g of water, and the solution has initially been at 200

C froze at

-0.240

C. Calculate the percentage dissociation of the salt.

 (Given :Kf for water = 1.86 K kg /mol, Atomic mass: K = 39 u, Cl= 35.5 u)

11. State briefly the principles involved in the following operations in metallurgy. Give an

example.

(i) Hydraulic washing.

(ii) Zone refining.

1. A bag contains one red and three white balls. Find the probability distribution of the number of red balls if two balls are drawn randomly from the bag without replacement.

2. Two cards are drawn randomly from a pack of 52 cards one-by-one without replacement. What is the probability of getting the first card red and the second Jk?

1. Find the vector and the cartesian equations of the plane containing the point ?̂+ 2?̂− ?̂ and parallel to the lines ?⃗ = (?̂+ 2?̂+ 2?̂) + ?(2?̂− 3?̂+ 2?̂) = 0 and ?⃗ = (3?̂+ ?̂− 2?̂) + ?(?̂− 3?̂+ ?̂) = 0

2. If ?⃗ ≠ 0, ⃗⃗⃗ ?⃗. ?⃗⃗ = ?⃗. ?⃗, ?⃗ × ?⃗⃗ = ?⃗ × ?⃗, then show that ?⃗⃗ = ?⃗.

Solution: We have ?⃗. (?⃗⃗ − ?⃗) = 0 ⇒ (?⃗⃗ − ?⃗) = ⃗0⃗ or ?⃗ ⊥ (?⃗⃗ − ?⃗) ⇒ ?⃗⃗ = ?⃗ or ?⃗ ⊥ (?⃗⃗ − ?⃗) Also, ?⃗ × (?⃗⃗ − ?⃗) = ⃗0⃗ ⇒ (?⃗⃗ − ?⃗) = ⃗0⃗ or ?⃗ ∥ (?⃗⃗ − ?⃗) ⇒ ?⃗⃗ = ?⃗ or ?⃗ ∥ (?⃗⃗ − ?⃗) ?⃗ ??? ??? ?? ???ℎ ????????????? ?? (?⃗⃗ − ?⃗) ??? ???????? ?? (?⃗⃗ − ?⃗) Hence, ?⃗⃗ = ?⃗. 1 1 1 10. Find the shortest distance between the following lines: ?⃗ = (?̂+ ?̂− ?̂) + ?(2?̂+ ?̂+ ?̂) ?⃗ = (?̂+ ?̂+ 2?̂) + ?(4?̂+ 2?̂+ 2?̂)

1. Evaluate: ∫ |? 3 − 3? 2 + 2?|?? 2 −1 Solution: The given definite integral = ∫ |?(? − 1)(? − 2)|?? 2 −1 = ∫ |?(? − 1)(? − 2)|?? 0 −1 + ∫ |?(? − 1)(? − 2)|?? + ∫ |?(? − 1)(? − 2)|?? 2 1 1 0 = − ∫ (? 3 − 3? 2 + 2?)?? 0 −1 + ∫ (? 3 − 3? 2 + 2?)?? 1 0 − ∫ (? 3 − 3? 2 + 2?)?? 2 1 = −[ ? 4 4 − ? 3 + ? 2 ]−1 0 + [ ? 4 4 − ? 3 + ? 2 ]0 1 − [ ? 4 4 − ? 3 + ? 2 ]1 2 = 9 4 + 1 4 + 1 4 = 11 4

2. Find the foot of the perpendicular from the point (1, 2, 0) upon the plane x – 3y + 2z = 9. Hence, find the distance of the point (1, 2, 0) from the given plane. Solution: The equation of the line perpendicular to the plane and passing through the point (1, 2, 0) is ? − 1 1 = ? − 2 −3 = ? 2 The coordinates of the foot of the perpendicular are (? + 1, −3? + 2,2?) for some ? These coordinates will satisfy the equation of the plane. Hence, we have ? + 1 − 3(−3? + 2) + 2(2?) = 9 ⇒ ? = 1 The foot of the perpendicular is (2, -1, 2). Hence, the required distance = √(1 − 2) 2 + (2 + 1) 2 + (0 − 2) 2 = √14 ????

1. Humans have innate immunity for protection against pathogens that may enter the gut along with food. What are the two barriers that protect the body from such pathogens?

2. Water samples were collected at points A, B and C in a river segment near a sugar factory and tested for BOD level. The BOD levels of samples A, B and C were 400 mg/L, 480 mg/L and 8 mg/L, respectively. What is this indicative of? Explain why the BOD level gets reduced considerably at collection point C?

An ecologist studies an area with population A, thriving on unlimited resources and showing exponential growth, introducing populations B and C to the same area. What will affect the population A, B and C growth pattern when living together in the same habitat?

How do normal cells get transformed into cancerous neoplastic cells? Elaborate, giving three examples of inducing agents. OR A person is suffering from a high-grade fever. Which symptoms will help identify if they are suffering from Typhoid, Pneumonia or Malaria?

Some restriction enzymes break a phosphodiester bond on both the DNA strands, such that only one end of each molecule is cut, and these ends have regions of single-stranded DNA. BamH1is one such restriction enzyme which binds at the recognition sequence, 5’-GGATCC- 3’and cleaves these sequences just after the 5′- guanine on each strand.

 a. What is the objective of this action?

b. Explain how the gene of interest is introduced into a vector.

c. You are given the DNA shown below.

Read the passage given below.

I saw ‘Jaws’, the famous shark movie, the summer it came out, in 1975 and became paranoid about sharks. Though I kept swimming after Jaws, it was always with the vague fear that a shark’s teeth could tug on my leg at any moment. Never mind that there’d been only two shark bites since 1900 on the Connecticut coast, where I lived. Cite a point in evidence from the text to suggest that the writer’s post-Jaws fear was not justified. State any trait of the writer evident from lines 5-10 and provide a reason for your choice.

People thought the writer was ‘either brave or very stupid. Why did some people

think that he was ‘foolish’?

Following questions : 

(i) How did the man with the white face behave as he entered the carriage?

a. Excited and enthusiastic

b. Scared

c. Excited and nervous

d. showed no enthusiasm

(ii) What was the book’s name that the narrator was reading?

a. Fortnum Roscoe’s Dream States

b. Dream States

c. Dreams of the States

d. State of the Dream

Read the passage given below.

Changing food preferences have brought about rapid changes in the structure of the Indian diet. The rapid proliferation of multinational fast food companies and the influence of Western culture have replaced traditional home-cooked meals with ready-to-eat, processed foods, thus increasing the risk of chronic diseases in urban Indians. Based on your understanding of the passage, answer ANY SIX out of the seven questions below.

i. What does the researcher mean by ‘changing food preferences?

ii. Why was this survey on the food consumption of adolescents undertaken?

You are Natasha, residing in Pune. Your cousin from the same city is hosting your

grandmother’s eightieth birth anniversary and has extended an invite to you. He has

also requested your assistance with the arrangements needed. Draft a reply of acceptance

in not more than 50 words.

5. Attempt ANY FIVE of the six questions below within 40 words each.

i. Mistaken identity led to a discovery of a new one for the rattrap peddler.

How did this impact him?

ii. As the host of a talk show, introduce Rajkumar Shukla to the audience by

stating any two of his defining qualities.

You may begin your answer like this:

Meet Rajkumar Shukla, the man who played a pivotal role in the Champaran

Movement. He ……

iii. Adrienne Rich chose to express her silent revolt through her poem, Aunt

Jennifer’s Tigers, just as Aunt Jennifer did with her embroidery. Explain.

iv. Rationalise why Keats uses the metaphor ‘an endless fountain of immortal

drink’ in his poem, A Thing of Beauty.

v. How do you think Derry’s mother contributes to his sense of alienation and

isolation? (On the Face of It)

vi. Validate John Updike’s open-ended title, ‘Should Wizard Hit Mommy?’.

Give any two characteristics of stacks. 

(i) Expand the following:

 SMTP, XML

(ii) Out of the following, which is the fastest wired and wireless medium

transmission?

Infrared, coaxial cable, optical fibre,

microwave, Ethernet cable

Each question carries 3 marks

8. Julie has created a dictionary containing names and marks as key-value pairs of 6 students. Write a program with separate user-defined functions to perform the following operations:

● Push the keys (name of the student) of the dictionary into a

stack, where the corresponding value (marks) is more significant than

75.

● Pop and display the content of the pile.

For example:

If the sample content of the dictionary is as follows:

(3)

[4]

R={“OM”:76, “JAI”:45, “BOB”:89, “ALI”:65, “ANU”:90,

“TOM”:82}

The output from the program should be:

TOM ANU BOB OM

A table, ITEM has been created in a database with the following fields:

ITEMCODE, ITEMNAME, QTY, PRICE

Give the SQL command to add a new field, DISCOUNT (of type Integer), to the ITEM table.

(ii) Categorise the following commands into DDL and DML commands?

INSERT INTO, DROP TABLE, ALTER TABLE,

UPDATE…SET

Give two advantages and two disadvantages of star topology.

Management is essential for organisations that are

(a) Non-profit organisations

(b) Service organisations

(c) Social organisations

(d) All of the above 1 2

‘Twinkle Stars’ is a well-known resort for organising parties, especially for children. However, in the previous 6 months, its popularity has reduced considerably as a new resort with better ambience and facilities has opened within its vicinity.

Name the related feature of the business environment that has adversely influenced the business of ‘Twinkle Stars’.

 (a) Totality of external forces

(b) Dynamic nature

(c) Interrelatedness

(d) Uncertainty

Which best training method would you suggest so that employees can learn the process? The Style watch company is well known for its stylish watches. It performs various activities like market analysis, product designing, packaging, warehousing, labelling, advertising, pricing, promotion, and sales. The company maintains good customer relations through various customer service activities.

·         Name the concept related to the activities mentioned above.

·         Explain any two features of the activity identified above.

Esha started a company called ‘Fashion Wrap.’ with ten employees to gift pack items for their clients attractively and fashionably called it new style wrapping. The company did very well in its initial years. It paid off, and the company increased its production and expanded its product range with different features.

(a) Identify the concept used by Esha through which he was able to steer his company to greater heights.

(b) Also, explain any three points of importance of this concept.

Amba Rani works as a corporate event coordinator in an event management company. She has been made an overall official in charge of organising a marriage ceremony for one of the company’s clients. To ensure that the ceremony takes place successfully, she identifies the various activities involved. She divides the work into different task groups like an invitation, decoration committee, and reception committee. In the context of the above case:

(a) Identify the function of management being performed by Amba Rani.

 (b) Describe briefly the various steps involved in the performance of the function of management as identified in part (1) of the question.

Average Propensity to Consume can never be ………………………… (choose the

correct alternative)

a) positive

b) zero

c) more than one

d) less than one

Wealth is a ……………….concept whereas income is a …………………. concept.

(Fill up the blank with correct alternative)

a. stock, flow

b. flow, stock

c. stock, stock

d. flow, flow

In an economy, the value of Net Factor Income from Abroad is ₹ 200 crores, and the value of Factor Income to Abroad is ₹ 40 crores. Identify the value of Factor Income from Abroad. (Choose the correct alternative)

a) ₹ 200 crores

b) ₹ 160 crores

c) ₹ 240 crores

d) ₹ 180 crores

From the following data, calculate

(a) Gross Domestic Product at Factor Cost.

(b) Factor Income to Abroad

S No Particulars Amount (cr)

(i) Compensation of employees 800

(ii) Profits 200

(iii) Dividends 50

(iv) Gross national product at market price 1400

(v) Rent 150

(vi) Interest 100

17 Explain the concept of excess demand and the inflationary gap with the help of a diagram. Suggest any two measures to correct this situation.

Which industry received the major setback due to British rule.

a. Cement

b. Handicraft

c. Paper

d. Iron and steel

The role of RBI is reduced from regulator to facilitator of the financial sector. State

whether true or false.

What is meant by economic planning?

Explain any three priority environmental issues of India today.

(i) Why is it necessary to revalue the assets and liabilities in case of admission of a partner?

(ii) Land and Building (book value) ₹ 1,60,000 sold for ₹ 3,00,000 through a broker who charged a 2% commission. Journalise the transaction at the time of dissolution of the firm.

One of the partners in a partnership firm has withdrawn ₹ 9,000 at the end of each quarter. Calculate interest on drawings at the rate of 6% per annum.

Jan Dhan Bank, an All India Financial Institution, had 10,000, 12 % debentures of ₹ 100 each, outstanding as of 31st March 2017. These debentures were due for redemption on 30th June 2018. Pass necessary Journal Entries for the redemption of debentures. Also, state the amount of Debenture Redemption Reserve to be created for redemption.

Mudit, Sudhir and Uday are partners in firm sharing profits in the ratio of 3:1:1. Their fixed capital balances are ₹ 4,00,000, ₹ 1,60,000, and ₹1,20,000 respectively.Net profit for the year ended 31st March 2018 distributed amongst the partners was ₹1,00,000, without taking into account the following adjustments: 

a) Interest on capitals @ 2.5% p.a.; 

b) Salary to Mudit ₹ 18,000 p.a. and commission to Uday ₹ 12,000 

c) Mudit was allowed a commission of 6% of divisible profit after charging such commission.