HSC Board Pattern Chemistry Mock Test-4

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Maharashtra HSC Board Pattern • Preliminary Examination

Chemistry: Full Syllabus Mock Test 4

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]

1. Which of the following is an amorphous solid?
   (A) Diamond

   (B) Glass

   (C) Sodium chloride

   (D) Graphite
2. The van't Hoff factor ($i$) for a dilute aqueous solution of Potassium sulfate ($K_2SO_4$) is approximately:
   (A) 1

   (B) 2

   (C) 3

   (D) 4
3. Which of the following is an extensive property?
   (A) Temperature

   (B) Density

   (C) Refractive index

   (D) Heat capacity
4. The SI unit of molar conductivity ($\Lambda_m$) is:
   (A) $\text{S m}^{-1}$

   (B) $\text{S m}^2 \text{ mol}^{-1}$

   (C) $\text{S m}^2$

   (D) $\Omega^{-1} \text{ cm}^{-1}$
5. The molecularity of an elementary reaction $2A \rightarrow \text{Products}$ is:
   (A) 0

   (B) 1

   (C) 2

   (D) 3
6. Which of the following Lanthanoids exhibits a +4 oxidation state?
   (A) Cerium (Ce)

   (B) Europium (Eu)

   (C) Lutetium (Lu)

   (D) Promethium (Pm)
7. EDTA (Ethylenediaminetetraacetate) is an example of a:
   (A) Unidentate ligand

   (B) Bidentate ligand

   (C) Tetradentate ligand

   (D) Hexadentate ligand
8. The best reagent for converting an alcohol into an alkyl chloride without separating by-products is:
   (A) $HCl / ZnCl_2$

   (B) $PCl_3$

   (C) $PCl_5$

   (D) $SOCl_2$
9. The major product formed in the Reimer-Tiemann reaction of phenol is:
   (A) Salicylic acid

   (B) Salicylaldehyde

   (C) Benzoquinone

   (D) Picric acid
10. The pyrimidine base present in DNA but absent in RNA is:
    (A) Adenine

    (B) Guanine

    (C) Uracil

    (D) Thymine

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

1. Define: Boiling point of a liquid.
2. What is a galvanic (voltaic) cell?
3. Write the integrated rate law equation for a zero-order reaction.
4. Write the chemical formula of chromyl chloride.
5. What is a zwitterion?
6. Name the monomer used in the preparation of Neoprene rubber.
7. What is an ambidentate ligand?
8. What is a chiral carbon atom?

SECTION B

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

3. Distinguish between Isothermal process and Adiabatic process. (Any 2 points).
4. State Henry's law. What is the effect of pressure on the solubility of a gas in a liquid?
5. Calculate the spin-only magnetic moment of the $Fe^{2+}$ ion. (Atomic number of Fe = 26).
6. Draw the chemical structures of $IF_7$ and $ClF_3$.
7. Distinguish between a double salt and a coordination complex. (Any 2 points).
8. Write a short note on the Wurtz-Fittig reaction with a chemical equation.
9. Explain why phenol is acidic in nature.
10. What is the action of bromine water on aniline at room temperature? Write the chemical equation.
11. Distinguish between globular proteins and fibrous proteins. (Any 2 points).
12. What is vulcanization of rubber? Why is it necessary?
13. State any two principles of green chemistry.
14. Write any two uses of Neon gas.

SECTION C

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

15. Calculate the packing efficiency of a Body-Centered Cubic (BCC) unit cell.
16. A solution containing 3.0 g of a non-volatile solute in 100 g of water boils at $100.26^\circ\text{C}$. Calculate the molar mass of the solute. ($K_b$ for water = 0.52 K kg/mol, Boiling point of pure water = $100^\circ\text{C}$).
17. Derive the relationship between $\Delta H$ and $\Delta U$ for a chemical reaction involving gases.
18. Calculate the standard EMF of the following cell at 298 K:
    $Zn(s) | Zn^{2+}(0.1 \text{ M}) || Cu^{2+}(0.01 \text{ M}) | Cu(s)$
    Given: $E^\circ_{Zn} = -0.76 \text{ V}$ and $E^\circ_{Cu} = +0.34 \text{ V}$. Use the Nernst equation to find the cell potential.
19. Derive the integrated rate law equation for a first-order reaction.
20. Describe the preparation of Potassium Dichromate ($K_2Cr_2O_7$) from chromite ore. (Write only the necessary chemical equations).
21. On the basis of Valence Bond Theory (VBT), explain the geometry and magnetic property of the $[CoF_6]^{3-}$ complex. (Atomic number of Co = 27).
22. Describe the $S_N1$ mechanism for the alkaline hydrolysis of tert-butyl bromide.
23. Explain the Williamson synthesis for the preparation of ethers with a suitable example.
24. Write the chemical reactions for the preparation of ethylamine from:
    1. Nitroethane
    2. Acetonitrile
    3. Propionamide
25. Explain the preparation of Bakelite. State its classification based on structure.
26. Explain the Sol-Gel process for the synthesis of nanomaterials.

SECTION D

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

27. (a) State Kohlrausch's law of independent migration of ions and write one of its applications. [2 Marks]
    (b) Derive the relationship between standard cell potential ($E^\circ_{cell}$) and standard Gibbs free energy change ($\Delta G^\circ$). [2 Marks]
28. (a) Explain the Aldol condensation of acetaldehyde with a chemical equation. [3 Marks]
    (b) What is a racemic mixture? [1 Mark]
29. (a) Derive the expression for the maximum work ($W_{max}$) done by a system during an isothermal and reversible expansion of an ideal gas. [3 Marks]
    (b) What are copolymers? Give one example. [1 Mark]
30. (a) Describe the manufacture of Sulfuric acid ($H_2SO_4$) by the Contact process. (Write only the chemical equations). [3 Marks]
    (b) Draw the structure of $XeF_6$. [1 Mark]
31. (a) Define half-life of a reaction. Show that for a first-order reaction, the half-life is independent of the initial concentration. [2 Marks]
    (b) Calculate the effective atomic number (EAN) of Copper in $[Cu(NH_3)_4]^{2+}$. (Atomic number of Cu = 29). [2 Marks]

Self-Evaluation Guide

Solutions & Marking Scheme

Maximum Marks: 70

SECTION A [18 Marks]

Q1. Multiple Choice Answers [10 Marks]:

1. (B) Glass [1 M. The rest are crystalline solids]

2. (C) 3 [1 M. $K_2SO_4 \rightarrow 2K^+ + SO_4^{2-}$ (3 ions)]

3. (D) Heat capacity [1 M. It depends on the mass of the substance]

4. (B) $\text{S m}^2 \text{ mol}^{-1}$ [1 M]

5. (C) 2 [1 M. Two molecules of A are participating]

6. (A) Cerium (Ce) [1 M. Achieves stable $f^0$ configuration]

7. (D) Hexadentate ligand [1 M. 2 Nitrogen and 4 Oxygen donor sites]

8. (D) $SOCl_2$ [1 M. Darzen's method gives gaseous byproducts]

9. (B) Salicylaldehyde [1 M]

10. (D) Thymine [1 M. RNA contains Uracil instead]

Q2. Very Short Answers [8 Marks]:

1. Boiling point: The temperature at which the vapor pressure of a liquid becomes equal to the external atmospheric pressure. [1 M]

2. Galvanic cell: An electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy. [1 M]

3. Zero-order integrated rate law: $k = \frac{[A]_0 - [A]_t}{t}$. [1 M]

4. Chromyl chloride formula: $CrO_2Cl_2$. [1 M]

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

6. Monomer of Neoprene: Chloroprene (2-chloro-1,3-butadiene). [1 M]

7. Ambidentate ligand: A unidentate ligand containing two different donor atoms but coordinating through only one of them at a time (e.g., $NO_2^-$). [1 M]

8. Chiral carbon atom: A carbon atom that is bonded to four different atoms or groups of atoms. [1 M]

SECTION B [16 Marks] (Attempt Any 8)

Q3. Isothermal vs Adiabatic Process:

Isothermal Process	Adiabatic Process
Temperature of the system remains constant ($\Delta T = 0$).	Temperature of the system changes ($\Delta T \neq 0$).
Heat is exchanged with surroundings ($q \neq 0$).	No heat is exchanged with surroundings ($q = 0$).

[1 M for each point. Total 2 M]

Q4. Henry's Law & Pressure Effect:

Statement: The solubility of a gas in a liquid at a constant temperature is directly proportional to the partial pressure of the gas above the solution. [1 M]

Effect of Pressure: As pressure increases, the solubility of the gas in the liquid increases. [1 M]

Q5. Magnetic Moment of $Fe^{2+}$:

Electronic configuration of Fe (Z=26) is $[Ar] 3d^6 4s^2$. $Fe^{2+}$ is $[Ar] 3d^6$. [1/2 M]

In $3d^6$, there are 4 unpaired electrons ($n=4$). [1/2 M]

$\mu = \sqrt{n(n+2)} = \sqrt{4(6)} = \sqrt{24} \approx 4.90 \text{ B.M.}$ [1 M]

Q6. Structures of $IF_7$ and $ClF_3$:

$IF_7$: Pentagonal bipyramidal. (Central I, 5 F's in a pentagon, 2 axial). [1 M for drawing/description]

$ClF_3$: T-shaped. (Central Cl, 3 F's, 2 lone pairs on equatorial positions). [1 M for drawing/description]

Q7. Double Salt vs Coordination Complex:

• Double salts dissociate completely into simple ions in water; Coordination complexes do not dissociate completely (complex ion remains intact).
• Double salts lose their solid-state identity in solution; Coordination complexes retain their identity in solution.

[1 M for each point. Total 2 M]

Q8. Wurtz-Fittig Reaction:

A mixture of an alkyl halide and an aryl halide reacts with sodium metal in dry ether to form an alkylbenzene. [1 M]

$C_6H_5-Br + 2Na + Br-CH_3 \xrightarrow{\text{Dry Ether}} C_6H_5-CH_3 \text{ (Toluene)} + 2NaBr$ [1 M]

Q9. Acidic nature of Phenol:

Phenol is acidic because the O-H bond weakens due to electron withdrawal by the benzene ring. After losing a proton, the resulting phenoxide ion is highly stabilized by resonance, which shifts the equilibrium forward. [2 M]

Q10. Bromine water on Aniline:

Aniline reacts rapidly to form a white precipitate of 2,4,6-tribromoaniline. [1 M]

$C_6H_5NH_2 + 3Br_2(aq) \rightarrow C_6H_2Br_3NH_2 \downarrow + 3HBr$ [1 M]

Q11. Globular vs Fibrous Proteins:

• Globular: Polypeptides fold into spherical shapes; Fibrous: Polypeptides form parallel thread-like structures.
• Globular: Soluble in water (e.g., Insulin); Fibrous: Insoluble in water (e.g., Keratin).

[1 M for each point. Total 2 M]

Q12. Vulcanization of Rubber:

The process of heating natural rubber with sulfur (3-5%) to form 3D cross-links between polymer chains. [1 M]

Necessity: Natural rubber is soft, sticky, and has low tensile strength. Vulcanization makes it hard, non-sticky, and highly elastic. [1 M]

Q13. Principles of Green Chemistry (Any 2):

• Prevention of Waste: Prevent waste rather than treating it after formation.
• Atom Economy: Maximize incorporation of reactants into final products.
• Catalysis: Use catalysts to reduce energy and waste.

[1 M for each point. Total 2 M]

Q14. Uses of Neon gas:

• Used in discharge tubes and fluorescent bulbs for advertisement display (neon signs). [1 M]
• Used in voltage regulators and indicators. [1 M]

SECTION C [24 Marks] (Attempt Any 8)

Q15. Packing Efficiency of BCC:

In BCC, atoms touch along the body diagonal. $4r = \sqrt{3}a \implies a = \frac{4r}{\sqrt{3}}$. [1 M]

Volume of unit cell $V = a^3 = \frac{64r^3}{3\sqrt{3}}$. [1/2 M]

Volume of 2 atoms in BCC $= 2 \times \frac{4}{3}\pi r^3 = \frac{8}{3}\pi r^3$. [1/2 M]

P.E. $= \frac{\frac{8}{3}\pi r^3}{\frac{64r^3}{3\sqrt{3}}} \times 100 = \frac{\sqrt{3}\pi}{8} \times 100 \approx 68\%$. [1 M]

Q16. Molar Mass from Elevation in BP:

Given: $W_2 = 3.0\text{g}, W_1 = 100\text{g}, K_b = 0.52$. $\Delta T_b = 100.26 - 100 = 0.26\text{K}$. [1 M]

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

Calc: $M_2 = \frac{1000 \times 0.52 \times 3.0}{0.26 \times 100} = \frac{1560}{26}$ [1 M]

$M_2 = 60 \text{ g/mol}$. [1/2 M]

Q17. $\Delta H$ and $\Delta U$ Derivation:

Enthalpy $H = U + PV$. For a change at constant pressure, $\Delta H = \Delta U + P\Delta V = \Delta U + P(V_2 - V_1)$. [1 M]

Using ideal gas law for reactants/products: $PV_1 = n_1RT$ and $PV_2 = n_2RT$. [1 M]

$\Delta H = \Delta U + n_2RT - n_1RT \implies \Delta H = \Delta U + \Delta n_g RT$. [1 M]

Q18. Nernst Equation EMF Calculation:

1. $E^\circ_{cell} = 0.34 - (-0.76) = 1.10 \text{ V}$. $n = 2$. [1 M]

2. $E_{cell} = 1.10 - \frac{0.0592}{2} \log_{10}\left(\frac{[Zn^{2+}]}{[Cu^{2+}]}\right) = 1.10 - 0.0296 \log_{10}\left(\frac{0.1}{0.01}\right)$ [1 M]

3. $E_{cell} = 1.10 - 0.0296 \log_{10}(10) = 1.10 - 0.0296 = 1.0704 \text{ V}$. [1 M]

Q19. 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]

Convert to log10: $k = \frac{2.303}{t} \log_{10} \frac{[A]_0}{[A]_t}$. [1 M]

Q20. Preparation of $K_2Cr_2O_7$ from Chromite:

1. $4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \rightarrow 8Na_2CrO_4 + 2Fe_2O_3 + 8CO_2$ [1 M]

2. $2Na_2CrO_4 + H_2SO_4 \rightarrow Na_2Cr_2O_7 + Na_2SO_4 + H_2O$ [1 M]

3. $Na_2Cr_2O_7 + 2KCl \rightarrow K_2Cr_2O_7 \downarrow + 2NaCl$ [1 M]

Q21. VBT for $[CoF_6]^{3-}$:

$Co^{3+}$ is $3d^6$. $F^-$ is a weak field ligand, does not pair the 4 unpaired electrons. [1 M]

Uses outer orbitals (one 4s, three 4p, two 4d) $\rightarrow$ $sp^3d^2$ hybridization $\rightarrow$ Octahedral. [1 M]

Because of 4 unpaired electrons, it is strongly Paramagnetic. [1 M]

Q22. $S_N1$ Mechanism:

Two-step process. Rate $= k[(CH_3)_3C-Br]$. [1 M]

Step 1 (Slow): Cleavage forms planar tertiary carbocation $(CH_3)_3C^+$. [1 M]

Step 2 (Fast): $OH^-$ attacks from front or back, leading to a Racemic mixture. [1 M]

Q23. Williamson Synthesis:

Reaction of alkyl halide with sodium alkoxide to form ethers via $S_N2$ mechanism. [1.5 M]

$C_2H_5-Br + CH_3-O^-Na^+ \rightarrow C_2H_5-O-CH_3 + NaBr$ [1.5 M]

Q24. Preparation of Ethylamine:

1. $CH_3CH_2NO_2 + 6[H] \xrightarrow{Sn/HCl} CH_3CH_2NH_2 + 2H_2O$ [1 M]

2. $CH_3CN + 4[H] \xrightarrow{Na/C_2H_5OH} CH_3CH_2NH_2$ [1 M]

3. $CH_3CH_2CONH_2 + Br_2 + 4NaOH \xrightarrow{\Delta} CH_3CH_2NH_2 + Na_2CO_3 + 2NaBr + 2H_2O$ [1 M]

Q25. Preparation of Bakelite:

Phenol + Formaldehyde $\rightarrow$ Novolac (linear polymer). [1 M]

Novolac + hexamethylenetetramine $\xrightarrow{\Delta}$ Bakelite (3D cross-linked solid). [1 M]

Classification: Cross-linked / Network polymer. [1 M]

Q26. Sol-Gel Process:

1. Hydrolysis: Precursors form a colloidal solution (Sol). [1 M]
2. Polycondensation: Particles link to form a 3D network enclosing liquid (Gel). [1 M]
3. Calcination: Dried gel heated to form final nanomaterial. [1 M]

SECTION D [12 Marks] (Attempt Any 3)

Q27. (a) Kohlrausch's law [2 Marks] (b) $\Delta G^\circ$ Derivation [2 Marks]

(a) At infinite dilution, each ion migrates independently and makes its own definite contribution to total molar conductivity. [1 M]
Application: Used to calculate molar conductivity of weak electrolytes at infinite dilution. [1 M]

(b) Max electrical work = Decrease in Gibbs Free Energy: $-\Delta G^\circ = W_{elec}$. [1 M]
Electrical work = Charge $\times$ Potential = $nF \times E^\circ_{cell}$. Therefore, $\Delta G^\circ = -nFE^\circ_{cell}$. [1 M]

Q28. (a) Aldol Condensation [3 Marks] (b) Racemic Mixture [1 Mark]

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

(b) An equimolar mixture of two enantiomers which is optically inactive. [1 M]

Q29. (a) $W_{max}$ Derivation [3 Marks] (b) Copolymers [1 Mark]

(a) $dW = -P_{ex} dV$. For reversible, $P_{ex} \approx P$. So $dW = -P dV$. [1 M]
$W_{max} = -\int_{V_1}^{V_2} P \, dV = -\int_{V_1}^{V_2} \frac{nRT}{V} dV$. [1 M]
$W_{max} = -nRT \ln(V_2/V_1) = -2.303 nRT \log_{10}(V_2/V_1)$. [1 M]

(b) Polymers made from two or more different monomers (e.g., Buna-S). [1 M]

Q30. (a) Contact Process Equations [3 Marks] (b) $XeF_6$ Structure [1 Mark]

(a) 1. $S_8(s) + 8O_2(g) \rightarrow 8SO_2(g)$ [1 M]
2. $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ ($V_2O_5$) [1 M]
3. $SO_3(g) + H_2SO_4(l) \rightarrow H_2S_2O_7(l) \xrightarrow{H_2O} 2H_2SO_4(aq)$ [1 M]

(b) Distorted octahedral. (Draw hexagon with Xe in center, 6 Fs, 1 lone pair protruding). [1 M]

Q31. (a) Half-life Independence [2 Marks] (b) EAN of Cu [2 Marks]

(a) Half-life is the time for concentration to reduce to half. For first order, $t_{1/2} = \frac{0.693}{k}$. [1 M]
Since $[A]_0$ does not appear in this equation, $t_{1/2}$ is independent of initial concentration. [1 M]

(b) In $[Cu(NH_3)_4]^{2+}$, Z = 29. Oxidation state of Cu (X) = +2. [1 M]
Electrons from 4 $NH_3$ (Y) = $4 \times 2 = 8$. EAN = $29 - 2 + 8 = 35$. [1 M]

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