CBSE 12th Chemistry Question Paper 2022 (Set 1) with Answers

CBSE 12th Chemistry Question Paper 2022 (Set 1)

31 questions from this Grade 12 Chemistry paper. The first 5 questions are solved free; log in as a Grade 12 student to view all solutions.

Q1 short answer

Propanal to Propane

Solution

Propanal (CH3CH2CHO) can be converted to Propane (CH3CH2CH3) by Clemmensen reduction using Zn-Hg and conc. HCl or Wolff-Kishner reduction using NH2NH2 followed by KOH in ethylene glycol.

Q2 short answer

Ethanal to But-2-enal

Solution

Ethanal (CH3CHO) undergoes Aldol condensation in the presence of dilute NaOH to form 3-hydroxybutanal, which upon heating loses a water molecule to form But-2-enal (CH3CH=CHCHO).

Q3 short answer

Ethanoic acid to ethanamide

Solution

Ethanoic acid (CH3COOH) reacts with ammonia (NH3) to form ammonium ethanoate (CH3COONH4), which upon strong heating undergoes dehydration to form Ethanamide (CH3CONH2).

Q4 short answer

rate of reaction, and

Solution

The rate of a reaction is defined as the change in concentration of any one of the reactants or products per unit time. Mathematically, for a general reaction aA + bB -> cC + dD, it is expressed as: Rate = -(1/a)(d[A]/dt) = -(1/b)(d[B]/dt) = (1/c)(d[C]/dt) = (1/d)(d[D]/dt).

Q5 short answer

rate of disappearance of H2 (g).

Solution

The rate of disappearance of H2(g) is defined as the negative rate of change of its molar concentration over time: Rate of disappearance of H2 = -d[H2]/dt.

Q5 short answer 3 marks

Calculate the emf of the following cell : Zn (s)|Zn2+ (0·01 M) || (0·001 M) Ag+|Ag (s) Given : Zn/Zn2+ E = 0·76 V and Ag+/Ag E = + 0·80 V [log 2 = 0·3010, log 3 = 0·4771, log 10 = 1]

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Q6 short answer

Calculate the degree of dissociation ( ) of CH3COOH if and of CH3COOH are 48 S cm2 mol 1 and 400 S cm2 mol 1respectively.

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Q7 short answer 3 marks

Write the hybridisation and magnetic character of the following complexes : (i) [NiCl4]2- (ii) [Co(NH3)6]3+ (iii) [FeF6]3- [Atomic number : Ni = 28, Co = 27, Fe = 26]

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Q7 short answer 3 marks

EH$ àW_ H$mo{Q> H$s A{^{H«$`m H$mo 75% {d`moOZ hmoZo _| 30 {_ZQ> bJVo h¢ & t1/2 H$s JUZm H$s{OE & 3{X`m J`m h¡ : [log 2 = 0·3, log 3 = 0·48, log 4 = 0·6, log 5 = 0·7]

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Q7 short answer 3 marks

A first order reduction takes 30 minutes for 75% decomposition. Calculate t1/2. Given : [log 2 = 0·3, log 3 = 0·48, log 4 = 0·6, log 5 = 0·7]

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Q8 short answer 3 marks

(i) Write the IUPAC name of the following complex : [Co(NH3)4(H2O)Cl]Cl2 (ii) What is the difference between an Ambidentate ligand and a Bidentate ligand ? (iii) Out of [Fe(NH3)6]3+ and [Fe(C2O4)3]3-, which complex is more stable and why ?

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Q11 short answer 1 mark

Write the major products in the following : (i)

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Q12 short answer

Oxidation of propanal is easier than propanone. Why ?

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Q13 short answer

How can you distinguish between Acetophenone and Benzophenone ?

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Q14 short answer 1 mark

Draw the structure of the following derivative : 2,4-Dinitrophenylhydrazone of Propanone

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Q16 short answer 3 marks

Write three differences between Lyophobic sol and Lyophilic sol.

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Q17 short answer

What is the cause of Brownian movement in colloidal particles ?

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Q18 short answer 1 mark

Why does physisorption decrease with increase in temperature ?

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Q19 short answer 1 mark

Why is E°(Mn2+/Mn) value highly negative as compared to other elements?

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Q20 short answer 1 mark

What is the reason for the irregularity in the above E° values?

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Q21 short answer 1 mark

Why is E°(Cu2+/Cu) value exceptionally positive?

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Q22 short answer 1 mark

Write the equation involved in the following reactions: Rosenmund reduction

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Q23 short answer 3 marks

Which acid of each pair would you expect to be stronger ? Give reason. (I) CH3COOH or FCH2COOH (II) OH or CH3COOH

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Q24 short answer

Distinguish between Pentan-2-one and Pentan-3-one.

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Q25 short answer 1 mark

Account for the following: Transition metals and their compounds show catalytic activities.

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Q26 short answer 1 mark

Account for the following: Zn, Cd and Hg are non-transition elements.

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Q27 short answer 1 mark

Account for the following: Zr and Hf are of almost identical atomic radii.

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Reading Passage

Amines constitute an important class of organic compounds derived by replacing one or more hydrogen atoms of ammonia molecule by alkyl/aryl groups. Amines are usually formed from nitro compounds, halides, amides, etc. They exhibit hydrogen bonding which influences their physical properties. Alkyl amines are found to be stronger bases than ammonia. In aromatic amines, electron releasing and withdrawing groups, respectively increase and decrease their basic character. Reactions of amines are governed by availability of the unshared pair of electrons on nitrogen. Influence of the number of hydrogen atoms at nitrogen atom on the type of reactions and nature of products is responsible for identification and distinction between primary, secondary and tertiary amines. Reactivity of aromatic amines can be controlled by acylation process.

Q28 short answer 1 mark

Why does aniline not give Friedel-Crafts reaction ?

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Q29 short answer 1 mark

Arrange the following in the increasing order of their pKb values : C6H5NH2 , NH3 , C2H5NH2 , (CH3 )3N

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Q30 short answer 1 mark

How can you distinguish between CH3CH2NH2 and (CH3CH2 )2NH by Hinsberg test ?

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Q31 short answer 2 marks

(a) Write the structures of A and B in the following reactions : (I) NO2 A B (II) CH3CH2CONH2 A B OR (b) How will you convert the following : (I) Benzoic acid to aniline (II) Aniline to p-bromoaniline

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