Class 12 Pre-Board Sample Paper 2024 Chemistry

2024

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SAMPLE QUESTION PAPER
1st PRE-BOARD (2023-24)
CHEMISTRY THEORY (043)

Class – XII Subject: Chemistry
Time: 3 Hours Max. Marks 70

General Instructions:
Read the following instructions carefully.
a) There are 34 questions in this question paper with internal choice.
b) SECTION A consists of 12 MCQ’s & 4 Assertions and Reasons carrying 1 mark each.
c) SECTION B consists of 8 very short answer questions carrying 2 marks each.
d) SECTION C consists of 5 short answer questions carrying 3 marks each.
e) SECTION D consists of 2 case- based questions carrying 4 marks each.
f) SECTION E consists of 3 long answer questions carrying 5 marks each.
g) All questions are compulsory.
h) Use of log tables and calculators is not allowed

S.No. SECTION – A Marks

1. The difference between the electrode potentials of two electrodes when no current 1
is drawn through the cell is called
(i) Cell potential (ii) Cell emf (iii) Potential difference (iv) Cell voltage
2. EᶱCr2O72-/Cr3+ = 1.33V, EᶱMnO4–/Mn2+ = 1.51V 1
EᶱCl2/Cl– = 1.36V, EᶱCr3+/Cr = -0.74V
Using the given data, which option is correct to the order of reducing power.
(i) Cr3+ < Cl– < Mn2+ < Cr
(ii) Mn2+ < Cl– < Cr3+ < Cr
(iii) Cr3+ < Cl– < Cr2O72– < MnO4–
(iv) Mn2+ < Cr3+ < Cl– < Cr
3. Activation energy of a chemical reaction can be determined by 1
(i) determining the rate constant at standard temperature.
(ii) determining the rate constants at two temperatures.
(iii) determining the probability of collision.
(iv) using catalyst.

4. The rate law for the reaction A + 2B → C is found to be Rate = k [A][B]. 1
The concentration of reactant ‘B’ is doubled, keeping the concentration of ‘A’
constant, the value of rate constant will be
(i) the same (ii) doubled (iii) quadrupled (iv) halved
5. Electronic configuration of a transition element X in +3 oxidation state is 1
[Ar]3d5. What is X?

(i) Manganese (ii) Iron (iii) Cobalt (iv) Chromium
6. The correct IUPAC name of [Pt (NH3)2Cl2] is 1
(i) Diamminedichloridoplatinum (II)
(ii) Diamminedichloridoplatinum (IV)
(iii) Dichloridodiammineplatinum (II)
(iv) Dichloridodiammineplatinum (IV)
7. Indicate the complex ion which shows geometrical isomerism. 1
(i) [Cr (H2O)4Cl2] +
(ii) [Pt (NH3)3 Cl]
(iii) [Co (NH3)6]3+
(iv) [Co (CN)5(NC)]3–
8. The order of reactivity of following alcohols with halogen acids is 1
A = Porapan-1-ol, B = Butan-2-ol, C = 2-methylbutan2-ol
(i) (A) > (B) > (C)
(ii) (C) > (B) > (A)
(iii) (B) > (A) > (C)
(iv) (A) > (C) > (B)
9. Which type of the reaction involves in the process of converting alkyl halides into 1
alcohols.
(i) addition reaction
(ii) substitution reaction
(iii) dehydrohalogenation reaction
(iv) rearrangement reaction
10. Which of the following products are obtained when methylamine reacts with 1
nitrous acid.
(i) CH3—O—N==O, NH3
(ii) CH3—O—CH3, H2
(iii) CH3OH, N2
(iv) CH3CHO, C2H6
11. which of the following reagent is not correct for the reduction of nitrobenzene 1
gives aniline?
(i) Sn/HCl (ii) Fe/HCl (iii) H2-Pd (iv) Sn/NH4OH
12. Which of the following acid is present in vitamin C? 1

(i) Aspartic acid (ii) Ascorbic acid
(iii) Adipic acid (iv) Saccharic acid
Q. No. 13 – 16, two statements are given—one labelled Assertion (A) and the
other labelled Reason (R). Select the correct option as given below:
(a) Both (A) and (R) are correct and (R) is correct explanation of (A).
(b) Both (A) and (R) are correct but (R) is not correct explanation of (A).

(c) (A) is correct, but (R) is incorrect statement.
(d) (A) is incorrect, but (R) is correct statement.
13. Assertion (A): In transition elements ns orbital is filled up first and (n – 1) d 1
afterwards, during ionization ns electrons are lost prior to (n–1) d electrons.
Reason (R): The effective nuclear charge felt by (n – 1) d electrons is higher as
compared to that by ns electrons.
14. Assertion (A): KCN reacts with methyl chloride to give methyl isocyanide. 1
–
Reason (R): CN is an ambident nucleophile.
15. Assertion (A): The boiling point of ethanol is higher than methoxymethane. 1
Reason (R): There is intramolecular hydrogen bonding in ethanol.
16. Assertion (A): Aromatic primary amines cannot be prepared by Gabriel 1
phthalimide synthesis.
Reason (R): Aryl halides do not undergo nucleophilic substitution with the anion
formed by phthalimide.
SECTION - B

17. Calculate ∆rGo and log Kc for the following reaction: 2
Cd2+(aq) + Zn(s) →Zn2+(aq) + Cd(s)
Given: E0Cd2+ /Cd = – 0.403 V, E0Zn2+/Zn = – 0.763 V
18. After 24 hrs, only 0.125 gm out of the initial quantity of 1 gm of a radioactive 2
isotope remains behind. What is its half-life period?
19. When a coordination compound CrCl3.6H2O is mixed with AgNO3, 2 moles of 2
AgCl are precipitated per mole of the compound.
Write (i) structural formula of the complex. (ii) IUPAC name of the complex.
20. Give reasons for the following: 2
(i) Chloroethane is insoluble in water.
(ii) Thionyl chloride method is preferred for preparing alkyl chlorides from
alcohols.
21. (i) Which alkyl halide from the following pair is chiral and undergoes faster SN2 2
reaction?
(a) CH3CH2CH2CH2Br (b) CH2CH(Br)CH2CH3
(ii) Out of SN1 and SN2, which reaction occurs with
(a) Inversion of configuration (b) Racemisation
22. Answer the followings: 2
(i) Among HI, HBr, HCl, HI is most reactive towards alcohols. Why?
(ii) Of the two alcohols;
(a) CH2—CH—CH2OH and (b) CH2—CH—CH2—CH2OH, which one will react
more easily with conc. HCl in the presence of ZnCl2?
23. Write the mechanism of the following reaction: 2

24. (i) What type of linkage is present in nucleic acids? 2
(ii) Give one example each for fibrous protein and globular protein.
SECTION - C

25. A solution containing 1.9 g per 100 mL of KCl (M = 74.5 g mol–1) is isotonic 3
with a solution containing 3 g per 100 mL of urea (M = 60 g mol–1). Calculate the

degree of dissociation of KCl solution. Assume that both the solutions have same
temperature.
26. (a) Define order of reaction. 3
(b) The rate of reaction, 2NO + Cl2 →2NOCl is doubled when concentration of
Cl2 is doubled and it becomes eight times when concentration of both NO and Cl2
are doubled. Deduce the order of the reaction.
27. Using valence bond theory, predict the hybridisation and magnetic character of 3
the following:
(i) [Co F6] 3–
(ii) [Ni (CN)4] 2–
(iii) [Fe (CN)6] 4–
[Atomic numbers: Fe = 26, Co = 27, Ni = 28]
28. (i) Account for the following: 3
(a) Cl—CH2COOH is a stronger acid than CH3COOH.
(b) Carboxylic acids do not give reactions of carbonyl group.
(ii) Out of CH3CH2—CO—CH2—CH3 and CH3CH2—CH2—CO—CH3, which
gives iodoform test?
OR
(i) Give reasons:
(a) The α-hydrogen of aldehydes and ketones are acidic in nature.
(b) Propanone is less reactive than ethanal towards addition of HCN.
(ii) Give a simple chemical test to distinguish between propanal and propanone.
29. (i) Which of the following biomolecules is insoluble in water? Justify. 3
Insulin, Haemoglobin, Keratin.
(ii) Name the protein and its shape present in oxygen carrier in human body.
(iii) Write chemical reaction to show that glucose contains aldehyde as carbonyl
group.
SECTION - D

30. Read the given passages and answer the questions that follow. 4
The spontaneous flow of the solvent through a semipermeable membrane from a
pure solvent to a solution or from a dilute solution to a concentrated solution is
called osmosis. The phenomenon of osmosis can be demonstrated by taking two
eggs of the same size. In an egg, the membrane below the shell and around the
egg material is semi-permeable. The outer hard shell can be removed by putting
the egg in dilute hydrochloric acid. After removing the hard shell, one egg is
placed in distilled water and the other in a saturated salt solution. After some time,
the egg placed in distilled water swells-up while the egg placed in salt solution
shrinks. The external pressure applied to stop the osmosis is termed as osmotic

pressure (a Colligative property). Reverse osmosis takes place when the applied
external pressure becomes larger than the osmotic pressure.
1. What happen when red blood corpuscles are placed in 0.5% NaCl solution?
2. Name one SPM which can be used in the process of reverse osmosis.
3. What are isotonic solutions? Which one of the following will have higher
osmotic pressure in 1 M KCl or 1 M urea solution?

31. Read the given passages and answer the questions that follow. 4
The most abundant biomolecules of the living system are proteins. They are
polymers of a-amino acids connected to each other by peptide linkage. Amino
acids contain amino (—NH2) and carboxyl (—COOH) group. Amino acids are
classified as acidic, basic or neutral depending upon the relative number of amino
and carboxyl groups in their molecule. They behave like salts rather than simple
amines or carboxylic acids. In aqueous solution, the carboxyl group can lose a
proton and amino group can accept a proton, giving rise to a dipolar ion known as
Zwitter ion. The amino acids, which can be synthesised in the body, are known as
non-essential amino acids. On the other hand, those which cannot be synthesised
in the body and must be obtained through diet, are known as essential amino
acids.
1. The Ka and Kb values of α-amino acid are very low. Why?
2. Draw the structure of Zwitter ion.
3. Name the alpha amino acid which is optically inactive and give any two
properties of amino acids.
SECTION - E

32. (i) Represent the cell in which the following reaction takes place: 5
2Al (s) + 3Ni2+ (0.1M) → 2Al3+ (0 01M) + 3Ni (s)
Calculate the emf if E0cell= 1.41 V.
(ii) How does molar conductivity vary with increase in concentration for strong
electrolyte and weak electrolyte? How can you obtain limiting molar
conductivity (ꓥ0m) for weak electrolyte?
OR
(i) Calculate Eo cell for the following reaction at 298 K:
2Al (s) + 3Cu2+ (0.1M) → 2Al3+ (0 01M) + 3Cu (s), Given: Ecell = 1.98 V
(ii) Define the following terms:
(a) Limiting molar conductivity
(b) Fuel cell and State two advantages over ordinary cell.
33. Assign reasons for the following: 5
(i) The enthalpies of atomisation of transition elements are high.
(ii) The transition metals and many of their compounds act as good catalysts.
(iii) From element to element, the actinoid contraction is greater than the
lanthanoid contraction.
(iv) The E0 value for the Mn3+/Mn2+ couple is much more positive than that of
Cr3+/Cr2+.

(v) Scandium (Z = 21) does not exhibit variable oxidation states and yet it is
regarded as a transition element.
OR
(i) Account for the following:
(a) Transition metals form large number of complex compounds.

(b) The lowest oxide of transition metal is basic whereas the highest oxide is
amphoteric or acidic.
(c) Why is Cu2+ ion coloured while Zn2+ ion is colourless in aqueous solution?
(ii) Describe the preparation of potassium permanganate from pyrolusite ore.
Write balanced chemical equation for one reaction to show the oxidizing nature of
potassium permanganate.
34. (i) A ketone ‘A’ which undergoes haloform reaction gives compound ‘B’ on 5
reduction. ‘B’ on heating with sulphuric acid gives compound ‘C’, which forms
mono-ozonide ‘D’. The compound ‘D’ on hydrolysis in presence of zinc dust
gives only acetaldehyde. Write the structures and IUPAC names of A, B and C.
Write down the reactions involved.
(ii) Predict the products formed when cyclohexane carbaldehyde reacts with
following reagents. (a) PhMgBr and then H3O+ (b) Tollens’ reagent.
OR
(i) Carry out the following conversions:
(a) p-nitrotoluene to 2-bromobenzoic acid
(b) Propanoic acid to acetic acid
(ii) An alkene ‘A’ with molecular formula C5H10 on ozonolysis gives a mixture of
two compounds, ‘B’ and ‘C’. Compound ‘B’ gives positive Fehling test and also
reacts with iodine and NaOH solution. Compound ‘C’ does not give Fehling
solution test but forms iodoform. Identify the compounds A, B and C.

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