ACADEMIC YEAR 2024-25

MODEL EXAMINATION 1
CHEMISTRY PAPER-1 (THEORY)

DATE:10.12.2024 GRADE: 12

Maximum Marks: 70
Time Allotted: Three Hours
Reading Time: Additional Fifteen minutes
➢ You are allowed a n additional 15 minutes for only reading the question
paper.
➢ It is divided into four sections and has 21 questions in all.
➢ All questions are compulsory. Answer all questions.
➢ Section A has fourteen subparts. Each question carries 1 mark.
➢ While attempting Multiple Choice Questions in Section A, you arerequired to
write only ONE option as the answer.
➢ Section B has ten questions. Each question carries 2 marks.
➢ Section C has seven questions. Each question carries 3 marks.
➢ Section D has three questions. Each question carries 5 marks.
➢ Internal choices have been provided in one question each in Sections B,C and D.
➢ Balanced equations must be given wherever possible and diagrams wherethey are
helpful.
➢ When solving numerical problems, all essential workings must be shown.
➢ In working out problems, use the following data:
Gas constant R=1·987cal deg-1mol-1=8·314JK-1mol-1
=0·0821dm3atmK-1mol-1, 1 l atm =1dm3atm=101·3 J.
1 Faraday=96500 coulombs. NA= 6·023×1023.

Instruction to Supervising Examiner

➢ Kindly read aloud the Instructions given above to all the candidates presentin the
examination hall.
Page 1 of 9
 SECTION A- 14 MARKS
Question 1
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the brackets: [4]
[addition, decrease, mole, sp3d2, d2sp3, substitution, lanthanoids, gram-equivalent, electronic, low,
volume, high, transition elements, increase, resonance]
(i) Equivalent conductivity is the conducting power of all the ions furnished by one _____ of
an electrolyte present in definite _____ of the solution.
(ii) Inner orbital complexes involve _______ hybridization and are _______ spin complexes.
(iii) Aldehydes are more reactive than ketones in nucleophilic _______ reactions. This
depends on _______ and steric factors.
(iv) The basic strength of oxides and hydroxides of _________ decreases with ________ in
atomic number due to lanthanoid contraction.

(B) Select and write the correct alternative from the choices given below. [7]

(i) Among the following which is the strongest base?

(a) aniline (c) benzyl amine
(b) p-methyl aniline (d) p-nitro aniline

(ii) pure water boils at 373.15 K and nitric acid boils at 359.19 K. An azeotropic mixture of
water and nitric acid boils at 393.55 K. Distilling the azeotropic mixture will cause
(a) pure nitric acid to distill over first
(b) pure water to distill over first
(c) one of them to distill over with a small amount of the other.
(d) Both of them to distill over in the same composition.

(iii) In nucleic acids, the nucleotides are joined together by

(a) Glycosidic linkage (c) H-bonds
(b) Phosphodiester linkage (d) Weak intermolecular forces

(iv) The chelating agent used for treatment in lead poisoning is

(a) Desferrioxamine (c) EDTA
(b) Cis-platin (d) D-penicillamine

Page 2 of 9
 (v) The species that attacks benzene in the following is

(a) Cl- (c) AlCl3

(b) AlCl4- (d) Cl+

(vi) Assertion (A): Ethyl bromide reacts with alc.KCN to form ethyl cyanide.
Reason (R) : KCN is a covalent compound.
(a) Both Assertion and reasoning are correct and the reason is the correct explanation of
the assertion.
(b) Both Assertion and reasoning are correct but the reason is not the correct explanation
of the assertion.
(c) Assertion is false and the reason is true.
(d) Assertion is true and the reason is false.

(vii) Assertion (A) : The standard reduction potential of copper is positive.

Reason (R) : Copper has high enthalpy of atomization and low enthalpy of hydration.
(a) Both Assertion and reasoning are correct and the reason is the correct explanation of
the assertion.
(b) Both Assertion and reasoning are correct but the reason is not the correct explanation
of the assertion.
(c) Assertion is false and the reason is true.
(d) Assertion is true and the reason is false.

(C) Read the passage carefully and answer the questions that follow. [3x1]

When lithium-ion is doped to well-ordered super lattices observed in graphite, polyacetylene, and
C60 hosts. In situ, resistivity measurements presented a 20-fold decrease upon doping, similar to
what is observed in graphite compounds. This can be explained by charge transfer between Li and
C again analogous to graphite intercalation compounds. The high reversible capacity and the high
rate performance of single wall carbon nanotubes suggest that they could offer some interest in Li-
ion battery applications.
[Reference: Journal of Electrochemical society]
Page 3 of 9
 (i) Is lithium-ion battery a primary or secondary cell?
(ii) Why so much interest for scientist in working with lithium compared to other metals?
(iii) What is the advantage of mercury cell over other batteries?

SECTION B - 20 MARKS
Question 2 [2]
(i) The vapour pressure of pure liquid X and pure liquid Y at 250C are 120 mm Hg and 160 mm
Hg respectively. If equal moles of X and Y are mixed to form an ideal solution, calculate the
vapour pressure of the solution.
OR
(ii) Visha took two aqueous solutions. One containing 7.5 g urea (molar mass = 60 g/mol) and the
other containing 42.75 g of the substance Z in 100 g of water, respectively. It was observed
that both the solutions frozen at the same temperature. Calculate the molar mass of Z.

Question 3 [2]
Consider the reduction of (R)-3-phenyl-2-pentanone by NaBH4. After the reduction is complete, it was
understood that two isomeric optically active compounds were formed and both were separated by
chromatographic technique. Identify the structure of these isomers and what is the stereochemical
relationship between them?

Question 4 [2]
Which alkyl halide would you expect to react more rapidly by an SN2 mechanism? Explain your answer
in each case.
(i) Ethyl bromide or iso-butylbromide
(ii) Chlorobenzene or 1-chlorobutane

Question 5 [2]
Observe the graph shown below and answer the following questions.

(i) What is order of reaction?

(ii) What is slope of the graph?
(iii)What is the relationship between ‘k’ and t1/2 for the above order?
Page 4 of 9
Question 6 [2]
An organic compound A on reaction with HBF4 gives organic compound B. Compound B on treatment
with NaNO2 and Cu with heating gives organic compound C. Organic compound C on reduction with
iron and HCl gives compound D with molecular formula C6H7N. D answers the carbylamine test
positively. Identify organic compounds A to D.

Question 7 [2]
The compound Co(en)2(NO2)2Cl has been prepared in three isomeric forms A and B and C. Compound A
does not react with silver nitrate solution and compound B reacts with silver nitrate and it is optically
active. Compound C reacts with silver nitrate but it is optically inactive. Identify the correct structures of
compound A, B and C and write their correct IUPAC names.

Question 8 [2]
Write the chemical test to distinguish between the following pairs of compounds.
(i) Benzaldehyde and propanal
(ii) Methanol and tert-butyl alcohol.

Question 9 [2]
Identify the structures A to D in the following reactions.

Question 10 [2]
When a steady current of 2 A was passed through two electrolytic cells A and B containing ZnSO4 and
CuSO4 connected in series, 2 g of copper was deposited. How long did the current flow? What mass of
zinc was deposited at the cathode of cell A? [Cu=63.5, Zn =65]

Question 11 [2]

Page 5 of 9
 SECTION C- 21 MARKS

Question 12 [3]
(i) Give balanced chemical equations for the following:
(a) Swart’s reaction
(b) Perkin’s reaction
(c) Coupling reaction with aniline

OR

(ii) Give balanced chemical equations for the following:

(a) Reaction between ethyl amine and acetyl chloride.
(b) Reaction between bromoethane and alc. AgNO2
(c) Reaction between acetyl chloride and dimethyl cadmium

Question 13 [3]
Solve the following numerical problems:
(i) A solution containing 0.2563 g of naphthalene (molecular mass = 128) in 50 g of carbon
tetrachloride yields a boiling point elevation of 0.201ºC while a solution of 0.6216 g of an
unknown solute in the same mass of the solvent gives a boiling point elevation of 0.647ºC.
Find the molecular mass of the unknown solute.
(ii) Find the elevation in boiling point of a solution of 13.44 g of CuCl2 assuming 100% ionization
in 1 kg of water. [RMM of CuCl2 = 134.4 g/mol, Kb = 0.52 K molal-1]

Question 14 [3]
Arrange the following as directed
(i) Iso-propyl alcohol, methyl alcohol, n-propyl alcohol (increasing order of boiling point)
(ii) Acetaldehyde, formaldehyde, acetone, di-isopropyl ketone (decreasing order of reactivity
towards nucleophilic addition)
(iii) Chlorobenzene, nitrobenzene, anisole, aniline, benzene (increasing order of reactivity towards
electrophilic bromination)

Page 6 of 9
Question 15 [3]
(i) Why [Co(en)3]3+ is more stable than [Co(NH3)6]3+?
(ii) Write formula of the following complex:
Dichloridobis(ethane-1,2-diamine)cobalt(III) ion.
(iii) Find the hybridization and magnetic behavior of the complex [Ni(CO)4]

Question 16 [3]
(i) Calculate the emf of the following cell at 298 K
Al(s)/ Al3+(0.001M) // Ni2+ (0.1M) /Ni (s)
Given E0 (Al3+/Al) = -1.66 V and E0 (Ni2+/Ni =-0.25 V)

(ii) A N/50 solution of a dibasic acid has a specific resistance of 2.16 x 103 ohm-cm at 180C.
Calculate the molar conductance and equivalent conductance of the solution.

Question 17 [3]
(i) Amino acids show amphoteric behavior. Why?
(ii) What is the basic structural difference between starch and cellulose?
(iii) Why vitamins B and C must be taken in diet regularly?

Question 18 [3]
(i) Phenol associates in benzene to form a dimer. A solution of 2.0 g phenol in 100 g of benzene
lowers its freezing point by 0.72 0C. Kf for benzene is 5.12 K molal-1. Calculate the degree
of association of phenol. [Mol.wt of phenol =94]
(ii) What type of deviation is shown by the solution of acetone and chloroform? Explain why they
form such a solution.

SECTION D - 15 MARKS
Question 19 [5]
(i) Answer the following questions:
(a) Based on the mechanism of aldol condensation reaction answer the following:
1. Which is the slow step?
2. Name the intermediate formed in the process.
3. Write the IUPAC name of the alkene formed during the aldol condensation of acetone.

Page 7 of 9
 (b) Effect the following conversions:
1. Ethyl alcohol to acetaldehyde phenyl hydrazone
2. Anisole to benzene
OR

(ii) Answer the following questions:

(a) Give reasons for the following:
1. Aniline cannot be directly treated with nitration mixture to get o-nitro aniline.
2. Only a primary alkyl halide is used in the preparation of ether by Williamson’s
synthesis.

(b) Effect the following conversions:

1. Nitro benzene to chlorobenzene
2. Benzene to o-chloro benzaldehyde
3. Iso-propyl alcohol to propane.

Question 20 [5]
(i) Following data are obtained for the reaction
N2O5 → 2 NO2 + ½ O2
t/s 0 300 600

[N2O5] / mol L-1 1.6 x10-2 0.8 x 10-2 0.4 x 10-2

Show that it follows first order reaction.

(ii) Predict the order of the reaction in the given plots:

Page 8 of 9
 (iii) The rate of the reaction increases 3 times, when the temperature changes from 293 K to 303 K.
calculate the activation energy of the reaction.

Question 21 [5]
(i) Name the following:
(a) A lanthanide ion that acts as oxidizing agent
(b) A lanthanide ion that acts as reducing agent.
(ii) Calculate the value of magnetic moment for Fe3+ ion. [At.no. of Fe=26]
(iii) Why transition metals are widely used as catalysts?
(iv) Give balanced chemical equations for the following:
(a) Reaction between acidified dichromate and sodium nitrite solution.
(b) Reaction between KMnO4 and H2S in neutral medium,

Page 9 of 9