Full Syllabus Mock Test 5 (Final) - Class 12 Chemistry | Chemca.in

Maharashtra HSC Board Pattern • Preliminary Examination

Chemistry: Full Syllabus Mock Test 5 (Final)

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]

The percentage of empty space (void volume) in a body-centered cubic (BCC) unit cell is:

(A) 26%
(B) 32%
(C) 47.6%
(D) 68%
A mixture of ethanol and acetone exhibits:

(A) Ideal behavior
(B) Negative deviation from Raoult's law
(C) Positive deviation from Raoult's law
(D) Zero volume of mixing
The SI unit of entropy ($S$) is:

(A) $\text{J K}^{-1}$
(B) $\text{J mol}^{-1}$
(C) $\text{J K}^{-1} \text{ mol}^{-1}$
(D) $\text{kJ mol}^{-1}$
Which of the following electrodes is used as a secondary reference electrode?

(A) Standard Hydrogen Electrode
(B) Calomel Electrode
(C) Zinc Electrode
(D) Copper Electrode
For a first-order reaction, the graph of $\ln[A]_t$ versus time ($t$) gives a straight line with a slope equal to:

(A) $k$
(B) $-k$
(C) $-k / 2.303$
(D) $k / 2.303$
Which of the following is a radioactive halogen?

(A) Fluorine
(B) Iodine
(C) Astatine
(D) Bromine
Which of the following transition metal ions is colorless in an aqueous solution?

(A) $Ti^{3+}$
(B) $V^{3+}$
(C) $Fe^{2+}$
(D) $Zn^{2+}$
The most reactive alkyl halide towards the $S_N1$ mechanism is:

(A) $CH_3Cl$
(B) $CH_3CH_2Cl$
(C) $(CH_3)_2CHCl$
(D) $(CH_3)_3CCl$
Phenol, on distillation with zinc dust, yields:

(A) Benzene
(B) Toluene
(C) Benzaldehyde
(D) Cyclohexane
The monomer used in the preparation of Nylon-6 is:

(A) Adipic acid
(B) Hexamethylenediamine
(C) $\epsilon$-Caprolactam
(D) Chloroprene

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

What is an ideal solution?
Write the Nernst equation for a single electrode potential at 298 K.
Name the linkage present in Maltose.
Write the formula of the coordination complex: Potassium hexacyanoferrate(II).
What is the action of sodium metal on ethyl bromide in dry ether?
Name the enzyme that catalyzes the conversion of glucose into ethanol.
Write the general outer electronic configuration of Actinoids.
Define: Nanomaterial.

SECTION B

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

Distinguish between Paramagnetism and Diamagnetism. (Any 2 points).
Define Ebullioscopic constant ($K_b$) and state its SI unit.
State Kohlrausch's law and write its mathematical expression for infinite dilution.
Give reason: Transition metals exhibit variable oxidation states.
Draw the Fischer projection formulas for the optical isomers (enantiomers) of lactic acid.
Explain the Etard reaction for the preparation of benzaldehyde.
What is the action of nitrous acid ($HNO_2$) on aniline at low temperature (273 K)? Write the chemical equation.
Define Green Chemistry and state any one of its principles.
Calculate the effective atomic number (EAN) of Fe in $[Fe(CN)_6]^{3-}$. (Atomic number of Fe = 26).
How is phenol prepared from chlorobenzene (Dow's process)?
Write the chemical structures of the monomers used in the preparation of Terylene (Dacron).
Write any two biological functions of carbohydrates.

SECTION C

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

Derive the integrated rate law equation for a zero-order reaction.
Describe the construction and working of the standard Calomel electrode.
Explain the $S_N1$ mechanism for the alkaline hydrolysis of tert-butyl bromide.
Calculate the maximum work done ($W_{max}$) when 2 moles of an ideal gas expand isothermally and reversibly from a volume of 10 L to 20 L at 298 K. ($R = 8.314 \text{ J K}^{-1} \text{mol}^{-1}$).
Explain the Aldol condensation of Acetone (Propan-2-one) with a balanced chemical equation.
Describe the commercial preparation of Sulfuric acid ($H_2SO_4$) by the Contact process. (Write the necessary chemical equations).
How are primary, secondary, and tertiary amines distinguished using Hinsberg's reagent?
A substance crystallizes in an FCC lattice. Its edge length is 400 pm. Calculate the density of the crystal if its molar mass is 60 g/mol. ($N_A = 6.022 \times 10^{23} \text{ mol}^{-1}$).
On the basis of Valence Bond Theory (VBT), explain the geometry and magnetic property of the $[Co(NH_3)_6]^{3+}$ complex. (Atomic number of Co = 27).
What is a peptide linkage? Explain its formation with the example of Glycylalanine.
Explain the preparation of Nylon-6,6. Write the names of its monomers and the chemical equation.
Describe the anomalous behavior of Fluorine compared to other halogens. (Write any 3 points).

SECTION D

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

(a) Derive the relationship between the molar mass of a solute and the elevation of boiling point of a solution. [3 Marks]
(b) What is a semipermeable membrane? [1 Mark]
(a) Explain the Reimer-Tiemann reaction with a chemical equation. [2 Marks]
(b) Explain Williamson synthesis for the preparation of ethers with an example. [2 Marks]
(a) Derive the expression: $\Delta H = \Delta U + \Delta n_g RT$. [2 Marks]
(b) State the First Law of Thermodynamics and define a State Function. [2 Marks]
(a) Distinguish between Lanthanoids and Actinoids. (Any 3 points). [3 Marks]
(b) Write the general outer electronic configuration of the d-block elements. [1 Mark]
(a) A first-order reaction takes 20 minutes for 50% completion. Calculate the time required for 75% completion of the reaction. [3 Marks]
(b) Define: Half-life period of a reaction. [1 Mark]

Self-Evaluation Guide

Solutions & Marking Scheme

Maximum Marks: 70

SECTION A [18 Marks]

Q1. Multiple Choice Answers [10 Marks]:

1. (B) 32% [1 M. BCC packing efficiency is 68%, so empty space is 100 - 68 = 32%]

2. (C) Positive deviation from Raoult's law [1 M. H-bonds in ethanol break upon adding acetone]

3. (C) $\text{J K}^{-1} \text{ mol}^{-1}$ [1 M]

4. (B) Calomel Electrode [1 M]

5. (B) $-k$ [1 M. From $\ln[A]_t = -kt + \ln[A]_0$]

6. (C) Astatine [1 M]

7. (D) $Zn^{2+}$ [1 M. $3d^{10}$ configuration, no unpaired electrons]

8. (D) $(CH_3)_3CCl$ [1 M. Forms stable tertiary carbocation]

9. (A) Benzene [1 M]

10. (C) $\epsilon$-Caprolactam [1 M]

Q2. Very Short Answers [8 Marks]:

1. Ideal solution: A solution that obeys Raoult's law over the entire range of concentrations at a given temperature. [1 M]

2. Nernst eq for single electrode: $E = E^\circ - \frac{0.0592}{n} \log_{10} \frac{[\text{Product}]}{[\text{Reactant}]}$ OR $E = E^\circ - \frac{0.0592}{n} \log_{10} \frac{1}{[M^{n+}]}$. [1 M]

3. Linkage in Maltose: $\alpha$-1,4-glycosidic linkage. [1 M]

4. Formula: $K_4[Fe(CN)_6]$. [1 M]

5. Action of Na on ethyl bromide: Undergoes Wurtz reaction to form n-Butane. [1 M]

6. Enzyme: Zymase. [1 M]

7. Actinoid configuration: $[Rn] 5f^{0-14} 6d^{0-2} 7s^2$. [1 M]

8. Nanomaterial: A material having structural components with at least one dimension in the nanometer scale (1 to 100 nm). [1 M]

SECTION B [16 Marks] (Attempt Any 8)

Q3. Paramagnetism vs Diamagnetism:

Paramagnetism	Diamagnetism
Substances are weakly attracted by an external magnetic field.	Substances are weakly repelled by an external magnetic field.
Occurs due to the presence of one or more unpaired electrons.	Occurs when all electrons are completely paired.

[1 M for each point. Total 2 M]

Q4. Ebullioscopic Constant ($K_b$):

Definition: It is defined as the elevation in boiling point produced when exactly 1 mole of a non-volatile, non-electrolyte solute is dissolved in 1 kg of solvent. [1 M]

SI Unit: $\text{K kg mol}^{-1}$. [1 M]

Q5. Kohlrausch's Law:

Statement: At infinite dilution, each ion migrates independently of its co-ion and makes its own definite contribution to the total molar conductivity of an electrolyte. [1 M]

Expression: $\Lambda^\circ_m = x\lambda^\circ_+ + y\lambda^\circ_-$ (where $x, y$ are number of cations and anions). [1 M]

Q6. Variable Oxidation States:

Transition elements show variable oxidation states because the energy difference between the $(n-1)d$ orbitals and the $ns$ orbitals is very small. [1 M]

Hence, electrons from both $ns$ and $(n-1)d$ orbitals can easily participate in bond formation. [1 M]

Q7. Optical Isomers of Lactic Acid:

COOH
|
H - C - OH
|
CH₃
(d-Lactic acid)

COOH
|
HO - C - H
|
CH₃
(l-Lactic acid)

[1 M for each correct enantiomer structure. Total 2 M]

Q8. Etard Reaction:

Toluene is oxidized to benzaldehyde using chromyl chloride ($CrO_2Cl_2$) in a non-polar solvent like $CS_2$. It forms a brown complex, which upon acid hydrolysis yields benzaldehyde. [1 M]

$C_6H_5CH_3 + 2CrO_2Cl_2 \xrightarrow{CS_2} \text{Brown Complex} \xrightarrow{H_3O^+} C_6H_5CHO$ [1 M]

Q9. Action of $HNO_2$ on Aniline:

Aniline reacts with nitrous acid (from $NaNO_2 + HCl$) at 273 K to form a stable diazonium salt (Benzene diazonium chloride). This is the Diazotization reaction. [1 M]

$C_6H_5NH_2 + HNO_2 + HCl \xrightarrow{273 \text{ K}} C_6H_5N_2^+Cl^- + 2H_2O$ [1 M]

Q10. Green Chemistry:

Definition: The design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. [1 M]

Principle: Atom Economy - maximizing the incorporation of all materials used in the process into the final product. [1 M]

Q11. EAN of Fe in $[Fe(CN)_6]^{3-}$:

Z = 26. Oxidation state (X) = +3. [1 M]

Electrons from 6 $CN^-$ ligands (Y) = 12. EAN = $26 - 3 + 12 = 35$. [1 M]

Q12. Dow's Process:

Chlorobenzene is fused with aqueous NaOH at 623 K and 300 atm to form sodium phenoxide, which on acidification gives phenol. [1 M]

$C_6H_5Cl \xrightarrow{NaOH, 623 \text{ K, 300 atm}} C_6H_5ONa \xrightarrow{H^+} C_6H_5OH$ [1 M]

Q13. Monomers of Terylene:

1. Ethylene glycol: $HO-CH_2-CH_2-OH$ [1 M]

2. Terephthalic acid: $HOOC-C_6H_4-COOH$ [1 M]

Q14. Functions of Carbohydrates:

Serve as the primary energy source (glucose/glycogen). [1 M]
Serve as structural material for cell walls in plants (cellulose). [1 M]

SECTION C [24 Marks] (Attempt Any 8)

Q15. Zero-Order Integrated Rate Law:

Rate $= -\frac{d[A]}{dt} = k[A]^0 = k \implies d[A] = -k \cdot dt$. [1 M]

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

$kt = [A]_0 - [A]_t \implies k = \frac{[A]_0 - [A]_t}{t}$. [1 M]

Q16. Calomel Electrode:

Construction: It consists of a glass tube with a Pt wire dipped into a paste of mercury (Hg) and mercurous chloride ($Hg_2Cl_2$ - calomel). The rest of the tube is filled with a saturated solution of KCl. [1.5 M]

Working: It is a secondary reference electrode. Depending on the other half-cell, it acts as anode or cathode. Reaction (reduction): $Hg_2Cl_2(s) + 2e^- \rightleftharpoons 2Hg(l) + 2Cl^-(aq)$. [1.5 M]

Q17. $S_N1$ Mechanism:

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

Step 1 (Slow): Heterolytic 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]

Q18. Maximum Work Numerical:

Given: $n = 2\text{ mol}$, $V_1 = 10\text{ L}$, $V_2 = 20\text{ L}$, $T = 298\text{ K}$, $R = 8.314$. [1/2 M]

Formula: $W_{max} = -2.303 nRT \log_{10}(V_2/V_1)$ [1/2 M]

Calc: $W_{max} = -2.303 \times 2 \times 8.314 \times 298 \times \log_{10}(20/10)$ [1 M]

$W_{max} = -11412.3 \times \log_{10}(2) = -11412.3 \times 0.3010$

$W_{max} = -3435 \text{ J} = -3.435 \text{ kJ}$. [1 M]

Q19. Aldol Condensation of Acetone:

Two molecules of acetone condense in presence of $Ba(OH)_2$ to form Diacetone alcohol. [1 M]

$2CH_3COCH_3 \xrightarrow{Ba(OH)_2} CH_3-C(CH_3)(OH)-CH_2-CO-CH_3$ [1 M]

Heating causes loss of water to form Mesityl oxide ($CH_3-C(CH_3)=CH-CO-CH_3$). [1 M]

Q20. 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]

Q21. Hinsberg's Test:

Reagent: Benzenesulfonyl chloride ($C_6H_5SO_2Cl$). [1 M]

$1^\circ$ amine: Forms a sulfonamide that is soluble in alkali (due to acidic H). [1/2 M]
$2^\circ$ amine: Forms a sulfonamide that is insoluble in alkali (no acidic H). [1 M]
$3^\circ$ amine: Does not react with Hinsberg's reagent. [1/2 M]

Q22. Density Numerical:

Given: FCC $\implies z=4$. $a = 400 \text{ pm} = 4 \times 10^{-8} \text{ cm}$. $M = 60 \text{ g/mol}$. [1 M]

Formula: $\rho = \frac{z \cdot M}{a^3 \cdot N_A}$ [1 M]

Calc: $\rho = \frac{4 \times 60}{(4 \times 10^{-8})^3 \times 6.022 \times 10^{23}} = \frac{240}{64 \times 10^{-24} \times 6.022 \times 10^{23}} = \frac{240}{38.54}$

Answer: $\rho = 6.22 \text{ g/cm}^3$. [1 M]

Q23. VBT for $[Co(NH_3)_6]^{3+}$:

$Co^{3+}$ is $3d^6$. $NH_3$ is a strong field ligand, forces pairing of all 6 electrons into three 3d orbitals, leaving two 3d orbitals empty. [1 M]

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

Since all electrons are paired, it is Diamagnetic (inner orbital complex). [1 M]

Q24. Peptide Linkage & Glycylalanine:

An amide linkage ($-CO-NH-$) between two amino acids with loss of water. [1 M]

$H_2N-CH_2-COOH + H_2N-CH(CH_3)-COOH \xrightarrow{-H_2O}$

$H_2N-CH_2-CO-NH-CH(CH_3)-COOH$ (Glycylalanine) [2 M for reaction]

Q25. Nylon-6,6:

Monomers: Hexamethylenediamine and Adipic acid. [1 M]

Preparation: They undergo condensation polymerization under high pressure and temperature (553 K) with elimination of water. [1 M]

$n(H_2N-(CH_2)_6-NH_2) + n(HOOC-(CH_2)_4-COOH) \xrightarrow{\Delta} [-NH-(CH_2)_6-NH-CO-(CH_2)_4-CO-]_n + 2nH_2O$ [1 M]

Q26. Anomalous Behavior of Fluorine:

Fluorine exhibits only a -1 oxidation state, while others show +1, +3, +5, +7. [1 M]
Fluorine cannot expand its octet because it lacks vacant d-orbitals. [1 M]
HF is a liquid due to hydrogen bonding, whereas other hydrogen halides are gases. [1 M]

SECTION D [12 Marks] (Attempt Any 3)

Q27. (a) Molar mass & BP Derivation [3 Marks] (b) Semipermeable membrane [1 Mark]

(a) $\Delta T_b \propto m \implies \Delta T_b = K_b \cdot m$. [1 M]
Molality $m = \frac{\text{moles of solute (} W_2 / M_2 \text{)}}{\text{mass of solvent in kg (} W_1 / 1000 \text{)}} = \frac{1000 \cdot W_2}{M_2 \cdot W_1}$. [1 M]
Substitute $m$: $\Delta T_b = \frac{1000 \cdot K_b \cdot W_2}{M_2 \cdot W_1} \implies M_2 = \frac{1000 \cdot K_b \cdot W_2}{\Delta T_b \cdot W_1}$. [1 M]

(b) A membrane that allows the passage of solvent molecules but strictly prevents the passage of solute molecules. [1 M]

Q28. (a) Reimer-Tiemann Reaction [2 Marks] (b) Williamson Synthesis [2 Marks]

(a) Phenol reacts with $CHCl_3$ and aqueous NaOH to form an intermediate, which on acid hydrolysis yields Salicylaldehyde. [1 M]
Phenol + $CHCl_3 + 3NaOH(aq) \xrightarrow{340 \text{ K}} \text{Intermediate} \xrightarrow{H_3O^+} \text{Salicylaldehyde}$. [1 M]

(b) Alkyl halide + Sodium alkoxide $\rightarrow$ Ether ($S_N2$ reaction). [1 M]
$C_2H_5Br + CH_3ONa \rightarrow C_2H_5-O-CH_3$ (Ethyl methyl ether) $+ NaBr$. [1 M]

Q29. (a) $\Delta H = \Delta U + \Delta n_g RT$ [2 Marks] (b) First Law & State Function [2 Marks]

(a) $H = U + PV \implies \Delta H = \Delta U + P\Delta V = \Delta U + P(V_2 - V_1)$. [1 M]
Using $PV=nRT$, $PV_1 = n_1RT$ and $PV_2 = n_2RT$. Thus, $\Delta H = \Delta U + (n_2 - n_1)RT = \Delta U + \Delta n_g RT$. [1 M]

(b) First Law: Energy is neither created nor destroyed, only transformed. [1 M]
State Function: A property whose value depends only on the current state of the system and not on the path followed (e.g., Enthalpy). [1 M]

Q30. (a) Lanthanoids vs Actinoids [3 Marks] (b) d-block configuration [1 Mark]

(a) [1 M each]
1. Progressive filling of 4f vs 5f orbitals.
2. Mostly non-radioactive vs All radioactive.
3. Show limited oxidation states (+3 mostly) vs show higher variable states (+3 to +7).

(b) $[Noble Gas] (n-1)d^{1-10} ns^{1-2}$. [1 M]

Q31. (a) $t_{75\%}$ Calculation [3 Marks] (b) Half-life definition [1 Mark]

(a) Given: $t_{1/2} = 20 \text{ min}$. $k = \frac{0.693}{20} = 0.03465 \text{ min}^{-1}$. [1 M]
For 75% completion, $[A]_0 = 100$, $[A]_t = 100 - 75 = 25$. [1/2 M]
$t_{75} = \frac{2.303}{k} \log\left(\frac{100}{25}\right) = \frac{2.303}{0.03465} \log(4) = \frac{2.303}{0.03465} \times 0.6020$. [1 M]
Answer: $t_{75} = 40 \text{ minutes}$ (or $2 \times t_{1/2}$). [1/2 M]

(b) The time required for the initial concentration of a reactant to reduce to half its value. [1 M]

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