Full Syllabus Mock Test 1 - Class 12 Chemistry | Chemca.in

Maharashtra HSC Board Pattern • Preliminary Examination

Chemistry: Full Syllabus Mock Test 1

Time: 3 Hours | Maximum Marks: 70

General Instructions:

The question paper is divided into four sections: A, B, C, and D.
Section A: Q. No. 1 contains 10 multiple-choice questions carrying 1 mark each. Q. No. 2 contains 8 very short answer type questions carrying 1 mark each.
Section B: Q. No. 3 to Q. No. 14 are short answer type questions carrying 2 marks each. Attempt any 8 questions.
Section C: Q. No. 15 to Q. No. 26 are short answer type questions carrying 3 marks each. Attempt any 8 questions.
Section D: Q. No. 27 to Q. No. 31 are long answer type questions carrying 4 marks each. Attempt any 3 questions.
Use of logarithmic tables is allowed. Use of calculator is not allowed.
Figures to the right indicate full marks.

SECTION A

Q1. Select and write the most appropriate answer from the given alternatives: [10 Marks]

Which of the following defects lowers the density of the crystal?

(A) Frenkel defect
(B) Schottky defect
(C) Interstitial defect
(D) F-centers
The unit of ebullioscopic constant ($K_b$) is:

(A) $\text{K kg mol}^{-1}$
(B) $\text{K mol kg}^{-1}$
(C) $\text{K kg}^{-1} \text{ mol}^{-1}$
(D) $\text{K mol}^{-1}$
What is the conjugate base of $HSO_4^-$?

(A) $H_2SO_4$
(B) $SO_4^{2-}$
(C) $H_3O^+$
(D) $H^+$
The work done when a gas expands into a vacuum (free expansion) is:

(A) Infinite
(B) Zero
(C) Maximum
(D) Minimum
The standard potential of a Standard Hydrogen Electrode (SHE) at 298 K is:

(A) 1.0 V
(B) 0.1 V
(C) exactly 0.00 V
(D) -1.0 V
The unit of the rate constant ($k$) for a first-order reaction is:

(A) $\text{s}^{-1}$
(B) $\text{mol L}^{-1} \text{ s}^{-1}$
(C) $\text{L mol}^{-1} \text{ s}^{-1}$
(D) $\text{L}^2 \text{ mol}^{-2} \text{ s}^{-1}$
Which of the following elements has the observed outer electronic configuration of $[Ar] 3d^5 4s^1$?

(A) Manganese (Mn)
(B) Chromium (Cr)
(C) Iron (Fe)
(D) Copper (Cu)
Which of the following reagents is used in the Swarts reaction to prepare alkyl fluorides?

(A) $NaI$ in dry acetone
(B) $SOCl_2$
(C) $AgF$
(D) $PCl_5$
To prepare an unsymmetrical ether via Williamson synthesis with good yield, the alkyl halide must be:

(A) Primary ($1^\circ$)
(B) Secondary ($2^\circ$)
(C) Tertiary ($3^\circ$)
(D) Vinylic
The monomer of natural rubber is:

(A) Chloroprene
(B) Neoprene
(C) Isoprene
(D) Styrene

Q2. Answer the following questions in one sentence: [8 Marks]

Define: Unit cell.
Write the mathematical expression for the first law of thermodynamics for an isothermal process.
State Kohlrausch's law of independent migration of ions.
Name the catalyst used in the commercial preparation of phenol from cumene.
What is a racemic mixture?
Name the product formed in the Stephen reaction before hydrolysis (i.e., the intermediate).
Define: Zwitterion.
What is the function of a salt bridge?

SECTION B

Attempt any EIGHT of the following questions: [16 Marks]

Distinguish between crystalline solids and amorphous solids. (Any 2 points).
State Henry's law. What is the effect of temperature on the solubility of a gas in a liquid?
Identify the Lewis acids and Lewis bases from the following: $NH_3, BF_3, AlCl_3, H_2O$.
Distinguish between Order and Molecularity of a reaction. (Any 2 points).
Draw the chemical structures of $XeF_2$ and $XeF_4$.
Calculate the spin-only magnetic moment of the $Co^{2+}$ ion. (Atomic number of Co = 27).
Write the IUPAC names of the following complexes: (i) $[Pt(NH_3)_2Cl_2]$ (ii) $K_3[Fe(C_2O_4)_3]$.
Explain the Finkelstein reaction with a suitable chemical equation.
Why is phenol more acidic than ethanol? Explain.
What is the action of $H_2 / Pd-BaSO_4$ (Rosenmund reduction) on acetyl chloride? Write the chemical equation.
Explain the Carbylamine test with a chemical equation.
What are biodegradable polymers? Give one example.

SECTION C

Attempt any EIGHT of the following questions: [24 Marks]

Derive the relationship between the density ($\rho$) of a unit cell and its edge length ($a$).
A solution containing 0.5126 g of naphthalene (molar mass 128 g/mol) in 50 g of carbon tetrachloride yields a boiling point elevation of 0.402 K. Calculate the molal elevation constant ($K_b$) of carbon tetrachloride.
Calculate the pH of a buffer solution containing 0.05 M $CH_3COOH$ and 0.01 M $CH_3COONa$. ($K_a$ for acetic acid = $1.8 \times 10^{-5}$).
Derive the relationship between $\Delta H$ and $\Delta U$ for a chemical reaction involving gases.
Calculate the EMF of the following cell at 298 K:
$Mg(s) | Mg^{2+}(0.1 \text{ M}) || Cu^{2+}(0.001 \text{ M}) | Cu(s)$
Given: $E^\circ_{Mg} = -2.37 \text{ V}$ and $E^\circ_{Cu} = +0.34 \text{ V}$.
Derive the integrated rate law equation for a first-order reaction.
Describe the manufacture of Sulfuric acid ($H_2SO_4$) by the Contact process. (Write only the necessary balanced chemical equations).
On the basis of Valence Bond Theory (VBT), explain the geometry and magnetic property of the $[NiCl_4]^{2-}$ complex. (Atomic number of Ni = 28).
Describe the $S_N2$ mechanism for the alkaline hydrolysis of methyl bromide.
Describe the preparation of phenol from cumene with necessary chemical equations.
Explain Gabriel Phthalimide Synthesis with the overall reaction sequence.
Distinguish between DNA and RNA. (Write any 3 points of distinction).

SECTION D

Attempt any THREE of the following questions: [12 Marks]

(a) Derive the relationship between half-life ($t_{1/2}$) and rate constant ($k$) for a first-order reaction. [2 Marks]
(b) A first-order reaction takes 40 minutes for 30% decomposition. Calculate its rate constant ($k$). [2 Marks]
(a) Explain the Aldol condensation of acetaldehyde with a chemical equation. [3 Marks]
(b) What are simple (symmetrical) ethers? [1 Mark]
(a) A solution of $CuSO_4$ is electrolyzed for 10 minutes with a current of 1.5 Amperes. Calculate the mass of copper deposited at the cathode. (Molar mass of Cu = 63.5 g/mol, $F = 96500 \text{ C mol}^{-1}$). [3 Marks]
(b) Define: Kohlrausch's law of independent migration of ions. [1 Mark]
(a) Calculate the Effective Atomic Number (EAN) of Cobalt in $[Co(NH_3)_6]^{3+}$. (Atomic number of Co = 27). [2 Marks]
(b) Write the names and structural formulas of the monomers used in the preparation of Nylon-6,6. [2 Marks]
(a) Calculate the percentage atom economy for the synthesis of Butyl bromide from the following reaction:
$C_4H_9OH + NaBr + H_2SO_4 \rightarrow C_4H_9Br + NaHSO_4 + H_2O$
(Given atomic masses: C=12, H=1, O=16, Na=23, Br=80, S=32). [2 Marks]
(b) State any two principles of Green Chemistry. [2 Marks]

Self-Evaluation Guide

Solutions & Marking Scheme

Maximum Marks: 70

SECTION A [18 Marks]

Q1. Multiple Choice Answers [10 Marks]:

1. (B) Schottky defect [1 M]

2. (A) $\text{K kg mol}^{-1}$ [1 M]

3. (B) $SO_4^{2-}$ [1 M]

4. (B) Zero [1 M]

5. (C) exactly 0.00 V [1 M]

6. (A) $\text{s}^{-1}$ [1 M]

7. (B) Chromium (Cr) [1 M]

8. (C) $AgF$ [1 M]

9. (A) Primary ($1^\circ$) [1 M]

10. (C) Isoprene [1 M]

Q2. Very Short Answers [8 Marks]:

1. Unit cell: The smallest repeating fundamental structural portion of a crystal lattice which, when repeated in 3D space, generates the entire lattice. [1 M]

2. First law for Isothermal: $q = -W$ (Since $\Delta U = 0$). [1 M]

3. Kohlrausch's law: At infinite dilution, each ion migrates independently of its co-ion and makes its own definite contribution to the total molar conductivity. [1 M]

4. Catalyst for Phenol: Cobalt naphthenate. [1 M]

5. Racemic mixture: An equimolar mixture of two enantiomers (dextro and laevo forms) which is optically inactive due to external compensation. [1 M]

6. Stephen reaction intermediate: Imine hydrochloride. [1 M]

7. Zwitterion: A dipolar, electrically neutral ion formed by internal proton transfer from a carboxyl group to an amino group in an amino acid. [1 M]

8. Salt bridge function: It connects the two half-cells to complete the inner circuit and maintains electrical neutrality. [1 M]

SECTION B [16 Marks] (Attempt Any 8)

Q3. Crystalline vs Amorphous solids:

Crystalline solids have a regular, long-range order; Amorphous have irregular, short-range order.
Crystalline have sharp melting points; Amorphous soften over a range of temperatures.

[1 M for each correct point. Total 2 M]

Q4. Henry's Law & Temperature Effect:

Statement: Solubility ($S$) of a gas in a liquid is directly proportional to the partial pressure ($P$) of the gas above the solution. ($S = K_H \cdot P$). [1 M]

Effect of Temp: Solubility of a gas in a liquid decreases with an increase in temperature (as dissolution is an exothermic process). [1 M]

Q5. Lewis Acids and Bases:

Lewis Acids (electron pair acceptors): $BF_3$, $AlCl_3$. [1 M]

Lewis Bases (electron pair donors): $NH_3$, $H_2O$. [1 M]

Q6. Order vs Molecularity:

Order is experimentally determined; Molecularity is a theoretical concept.
Order can be zero or fraction; Molecularity is always a whole number $\ge 1$.

[1 M for each correct point. Total 2 M]

Q7. Structures of $XeF_2$ and $XeF_4$:

$XeF_2$: Linear structure (3 lone pairs equatorial, 2 bond pairs axial). [1 M]

$XeF_4$: Square planar structure (2 lone pairs axial, 4 bond pairs equatorial). [1 M]

Q8. Magnetic Moment of $Co^{2+}$:

Configuration of $Co^{2+}$ ($Z=27$) is $[Ar] 3d^7$. It has 3 unpaired electrons ($n=3$). [1 M]

$\mu = \sqrt{n(n+2)} = \sqrt{3(5)} = \sqrt{15} = 3.87 \text{ B.M.}$ [1 M]

Q9. IUPAC Names:

(i) $[Pt(NH_3)_2Cl_2]$: Diamminedichloroplatinum(II) [1 M]

(ii) $K_3[Fe(C_2O_4)_3]$: Potassium trioxalatoferrate(III) [1 M]

Q10. Finkelstein Reaction:

Alkyl iodides are prepared by heating alkyl chlorides or bromides with NaI in dry acetone. [1 M]

$R-X + NaI \xrightarrow{\text{Dry Acetone}} R-I + NaX \downarrow$ [1 M]

Q11. Phenol vs Ethanol Acidity:

Phenol is more acidic because the phenoxide ion formed is highly stabilized by resonance (delocalization of negative charge). [1 M]

Ethanol's ethoxide ion lacks resonance, and the +I effect of the ethyl group destabilizes the anion. [1 M]

Q12. Rosenmund Reduction:

Acetyl chloride is reduced to acetaldehyde using Hydrogen gas over a Palladium catalyst supported on Barium sulfate. [1 M]

$CH_3COCl + H_2 \xrightarrow{Pd/BaSO_4} CH_3CHO + HCl$ [1 M]

Q13. Carbylamine Test:

Primary amines heated with chloroform and alc. KOH form foul-smelling isocyanides. [1 M]

$R-NH_2 + CHCl_3 + 3KOH(alc) \xrightarrow{\Delta} R-N \equiv C + 3KCl + 3H_2O$ [1 M]

Q14. Biodegradable Polymers:

Polymers that can be broken down into harmless substances by environmental microorganisms. [1 M]

Example: PHBV or Nylon-2-nylon-6. [1 M]

SECTION C [24 Marks] (Attempt Any 8)

Q15. Density Derivation:

Volume of cubic unit cell = $a^3$. [1/2 M]

Mass of unit cell = $z \times m$ (where $z$ = atoms per cell, $m$ = mass of one atom). [1/2 M]

Mass of one atom $m = \frac{M}{N_A}$ (where $M$ = Molar mass). [1 M]

$\rho = \frac{\text{Mass}}{\text{Volume}} = \frac{z \cdot (M / N_A)}{a^3} = \frac{z \cdot M}{a^3 \cdot N_A}$. [1 M]

Q16. $K_b$ Numerical:

Given: $W_2 = 0.5126\text{g}, M_2 = 128, W_1 = 50\text{g}, \Delta T_b = 0.402\text{K}$. [1/2 M]

Formula: $K_b = \frac{M_2 \cdot \Delta T_b \cdot W_1}{1000 \cdot W_2}$ [1/2 M]

Calc: $K_b = \frac{128 \times 0.402 \times 50}{1000 \times 0.5126} = \frac{2572.8}{512.6}$ [1 M]

Answer: $K_b = 5.019 \text{ K kg mol}^{-1}$. [1 M]

Q17. Buffer pH Numerical:

$pK_a = -\log(1.8 \times 10^{-5}) = 5 - \log(1.8) = 5 - 0.2553 = 4.7447$ [1 M]

$pH = pK_a + \log\frac{[\text{Salt}]}{[\text{Acid}]} = 4.7447 + \log\left(\frac{0.01}{0.05}\right)$ [1 M]

$pH = 4.7447 - \log 5 = 4.7447 - 0.6990 = 4.0457$. [1 M]

Q18. $\Delta H$ and $\Delta U$ Derivation:

$\Delta H = \Delta U + P\Delta V = \Delta U + P(V_2 - V_1)$. [1 M]

For ideal gases: $PV_1 = n_1RT$ and $PV_2 = n_2RT$. [1 M]

$\Delta H = \Delta U + (n_2 - n_1)RT \implies \Delta H = \Delta U + \Delta n_g RT$. [1 M]

Q19. Nernst Equation EMF Calculation:

$E^\circ_{cell} = 0.34 - (-2.37) = 2.71 \text{ V}$. Here $n = 2$. [1 M]

$E_{cell} = 2.71 - \frac{0.0592}{2} \log\left(\frac{0.1}{0.001}\right) = 2.71 - 0.0296 \log(100)$ [1 M]

$E_{cell} = 2.71 - 0.0296(2) = 2.6508 \text{ V}$. [1 M]

Q20. First-Order Integrated Rate Law:

Rate $= -\frac{d[A]}{dt} = k[A] \implies \frac{d[A]}{[A]} = -k \cdot dt$. [1 M]

Integrate from $[A]_0$ to $[A]_t$: $\ln[A]_t - \ln[A]_0 = -kt$. [1 M]

$kt = \ln\left(\frac{[A]_0}{[A]_t}\right) \implies k = \frac{2.303}{t} \log_{10} \frac{[A]_0}{[A]_t}$. [1 M]

Q21. Contact Process Equations:

1. $S_8(s) + 8O_2(g) \rightarrow 8SO_2(g)$ [1 M]

2. $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ ($V_2O_5$ catalyst) [1 M]

3. $SO_3(g) + H_2SO_4(l) \rightarrow H_2S_2O_7(l)$ (Oleum) $\xrightarrow{H_2O} 2H_2SO_4(aq)$ [1 M]

Q22. VBT for $[NiCl_4]^{2-}$:

$Ni^{2+}$ is $3d^8$. $Cl^-$ is a weak field ligand, no pairing occurs. [1 M]

Uses outer one 4s and three 4p orbitals $\rightarrow$ $sp^3$ hybridization $\rightarrow$ Tetrahedral geometry. [1 M]

Contains 2 unpaired electrons $\rightarrow$ Paramagnetic. [1 M]

Q23. $S_N2$ Mechanism:

Single-step concerted process. Nucleophile ($OH^-$) attacks carbon from the backside (opposite to Br). [1 M]

Forms a highly unstable pentacoordinate transition state. [1 M]

Results in 100% Walden inversion of configuration. [1 M]

Q24. Phenol from Cumene:

Oxidation: $C_6H_5CH(CH_3)_2 + O_2 \xrightarrow{\text{Co-naph}} C_6H_5C(OOH)(CH_3)_2$ (Cumene hydroperoxide). [1.5 M]

Hydrolysis: $C_6H_5C(OOH)(CH_3)_2 \xrightarrow{H^+} C_6H_5OH + CH_3COCH_3$ (Acetone). [1.5 M]

Q25. Gabriel Phthalimide Synthesis:

1. Phthalimide + alc. KOH $\rightarrow$ Potassium phthalimide. [1 M]

2. Potassium phthalimide + $R-X \rightarrow$ N-alkyl phthalimide. [1 M]

3. Hydrolysis $\rightarrow$ Pure primary amine ($R-NH_2$) + phthalic acid. [1 M]

Q26. DNA vs RNA:

Sugar: DNA has deoxyribose; RNA has ribose.
Bases: DNA has Thymine; RNA has Uracil.
Structure: DNA is double $\alpha$-helix; RNA is single stranded.

[1 M for each correct point. Total 3 M]

SECTION D [12 Marks] (Attempt Any 3)

Q27. (a) $t_{1/2}$ Derivation [2 Marks] (b) Numerical [2 Marks]

(a) $k = \frac{2.303}{t} \log\frac{[A]_0}{[A]_t}$. At $t = t_{1/2}, [A]_t = [A]_0/2$. [1 M]
$k = \frac{2.303}{t_{1/2}} \log(2) = \frac{2.303 \times 0.3010}{t_{1/2}} \implies t_{1/2} = \frac{0.693}{k}$. [1 M]

(b) $t = 40$, $[A]_0 = 100$, $[A]_t = 70$.
$k = \frac{2.303}{40} \log\left(\frac{100}{70}\right) = \frac{2.303 \times 0.1548}{40}$ [1 M]
Answer: $k = 0.00891 \text{ min}^{-1}$. [1 M]

Q28. (a) Aldol Condensation [3 Marks] (b) Simple Ethers [1 Mark]

(a) Two molecules of acetaldehyde (having $\alpha$-H) react in dil. NaOH to form Acetaldol, which on heating loses water to form Crotonaldehyde. [1 M]
$2CH_3CHO \xrightarrow{\text{dil. NaOH}} CH_3CH(OH)CH_2CHO \xrightarrow{\Delta, -H_2O} CH_3CH=CHCHO$. [2 M for equations]

(b) Ethers where both alkyl/aryl groups attached to oxygen are identical (e.g., $CH_3-O-CH_3$). [1 M]

Q29. (a) Electrolysis Mass [3 Marks] (b) Kohlrausch Law [1 Mark]

(a) $Q = I \times t = 1.5 \times 600 = 900 \text{ C}$. [1 M]
$W = \frac{M \times Q}{n \times F} = \frac{63.5 \times 900}{2 \times 96500}$ [1 M]
$W = 0.296 \text{ g}$. [1 M]

(b) At infinite dilution, each ion migrates independently and contributes to total molar conductivity. [1 M]

Q30. (a) EAN of Co [2 Marks] (b) Nylon-6,6 Monomers [2 Marks]

(a) Co in $[Co(NH_3)_6]^{3+}$ is +3. $Z=27, X=3, Y=12$.
EAN = $27 - 3 + 12 = 36$. [2 M]

(b) Hexamethylenediamine: $H_2N-(CH_2)_6-NH_2$ [1 M]
Adipic acid: $HOOC-(CH_2)_4-COOH$ [1 M]

Q31. (a) Atom Economy [2 Marks] (b) Green Chem Principles [2 Marks]

(a) Formula weight of $C_4H_9Br = 137$. Total weight of reactants $= 74 + 103 + 98 = 275$. [1 M]
$\% AE = \frac{137}{275} \times 100 = 49.81\%$. [1 M]

(b) 1. Prevention of waste. 2. Atom Economy. (Or Design for Degradation, Safer Solvents, etc.) [2 M for any two principles]

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