Full Syllabus Mock Test 3 - Class 12 Chemistry | Chemca.in

Maharashtra HSC Board Pattern • Preliminary Examination

Chemistry: Full Syllabus Mock Test 3

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 packing efficiency of a face-centered cubic (fcc) unit cell is:

(A) 52.4%
(B) 68%
(C) 74%
(D) 100%
Which of the following colligative properties is most suitable for determining the molar mass of polymers?

(A) Elevation in boiling point
(B) Depression in freezing point
(C) Relative lowering of vapor pressure
(D) Osmotic pressure
According to the first law of thermodynamics, for an adiabatic process:

(A) $\Delta U = q$
(B) $W = 0$
(C) $\Delta U = W$
(D) $q = W$
The oxidation state of Iron (Fe) in $[Fe(CN)_6]^{3-}$ is:

(A) +2
(B) +3
(C) +4
(D) +6
The unit of the rate constant for a zero-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 is the most basic amine in the gaseous phase?

(A) $NH_3$
(B) $CH_3NH_2$
(C) $(CH_3)_2NH$
(D) $(CH_3)_3N$
The reagent used to distinguish between primary, secondary, and tertiary alcohols is:

(A) Tollens' reagent
(B) Lucas reagent
(C) Hinsberg's reagent
(D) Grignard reagent
The monomer of Teflon is:

(A) Vinyl chloride
(B) Tetrafluoroethene
(C) Styrene
(D) Isoprene
The catalyst used in the manufacture of Sulfuric acid by the Contact process is:

(A) Finely divided iron
(B) Vanadium pentoxide ($V_2O_5$)
(C) $MnO_2$
(D) $AlCl_3$
Which of the following is an example of an ambidentate ligand?

(A) $H_2O$
(B) $NH_3$
(C) $SCN^-$
(D) $Cl^-$

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

Define: Osmosis.
Write the IUPAC name of Isopropyl alcohol.
State Kohlrausch's law of independent migration of ions.
What are F-centers in a crystal lattice?
Define: Order of a reaction.
What is a peptide bond?
Identify the product formed when methyl magnesium bromide is treated with dry ice and subsequently hydrolyzed.
Write the formula for calculating Percentage Atom Economy.

SECTION B

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

Distinguish between Ideal and Non-ideal solutions. (Any 2 points).
Calculate the Effective Atomic Number (EAN) of Iron in $[Fe(CN)_6]^{4-}$. (Atomic number of Fe = 26).
Write the chemical equation for the Reimer-Tiemann reaction.
What is the action of bromine water on aniline at room temperature? Write the chemical equation.
State Saytzeff's rule with a suitable example.
Write the names and structural formulas of the monomers used in the preparation of Nylon-6,6.
State any two applications of nanomaterials.
Derive the relationship between $\Delta H$ and $\Delta U$ for a chemical reaction involving gases.
The resistance of a conductivity cell filled with 0.1 M KCl solution is 100 $\Omega$. If the conductivity of 0.1 M KCl is 0.0129 S/cm, calculate the cell constant.
State any two anomalous properties of oxygen compared to other group 16 elements.
What is a salt bridge? Give its two functions.
Distinguish between Enantiomers and Diastereomers. (Any 2 points).

SECTION C

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

Describe the $S_N2$ mechanism for the alkaline hydrolysis of methyl bromide.
Describe the preparation of phenol from cumene with necessary chemical equations. Why is this method commercially preferred?
Derive the integrated rate law equation for a first-order reaction.
Define optical isomerism. Draw the optical isomers (enantiomers) of the complex ion $[Co(en)_3]^{3+}$.
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.
Explain Gabriel Phthalimide Synthesis with the overall reaction sequence.
Define carbohydrates. How are they classified based on their behavior towards hydrolysis? Give one example of each.
Describe the preparation of Potassium Dichromate ($K_2Cr_2O_7$) from chromite ore. (Write only the necessary chemical equations).
Explain the catalytic property and magnetic property of transition metals.
Derive the expression for the maximum work ($W_{max}$) done by a system during an isothermal and reversible expansion of an ideal gas.
Distinguish between $S_N1$ and $S_N2$ mechanisms. (Any 3 points).
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).

SECTION D

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

(a) 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 $E^\circ_{Cu} = +0.34 \text{ V}$. [3 Marks]
(b) What is meant by a secondary voltaic cell? [1 Mark]
(a) Explain the Aldol condensation of acetaldehyde with a chemical equation. [3 Marks]
(b) Write the IUPAC name of Acetone. [1 Mark]
(a) A first-order reaction takes 40 minutes for 30% decomposition. Calculate its half-life period. [3 Marks]
(b) What is a pseudo-first-order reaction? Give one example. [1 Mark]
(a) Describe the manufacture of Sulfuric acid ($H_2SO_4$) by the Contact process. (Write only the chemical equations). [3 Marks]
(b) Write the chemical formula of Oleum. [1 Mark]
(a) On the basis of Valence Bond Theory (VBT), explain the geometry and magnetic property of the $[Ni(CN)_4]^{2-}$ complex. (Atomic number of Ni = 28). [3 Marks]
(b) Define: Coordination Number. [1 Mark]

Self-Evaluation Guide

Solutions & Marking Scheme

Maximum Marks: 70

SECTION A [18 Marks]

Q1. Multiple Choice Answers [10 Marks]:

1. (C) 74% [1 M. FCC and HCP have the maximum packing efficiency]

2. (D) Osmotic pressure [1 M. Useful for macromolecules because it is measured at room temperature]

3. (C) $\Delta U = W$ [1 M. For adiabatic, $q=0$. By 1st law $\Delta U = q + W$]

4. (B) +3 [1 M. $x + 6(-1) = -3 \implies x = +3$]

5. (B) $\text{mol L}^{-1} \text{ s}^{-1}$ [1 M]

6. (D) $(CH_3)_3N$ [1 M. In gaseous phase, basicity strictly follows +I effect: $3^\circ > 2^\circ > 1^\circ$]

7. (B) Lucas reagent [1 M. Mixture of conc. HCl and anhydrous $ZnCl_2$]

8. (B) Tetrafluoroethene [1 M]

9. (B) Vanadium pentoxide ($V_2O_5$) [1 M]

10. (C) $SCN^-$ [1 M. Can coordinate through either S or N]

Q2. Very Short Answers [8 Marks]:

1. Osmosis: The spontaneous, unidirectional flow of solvent molecules through a semipermeable membrane from a pure solvent to a solution (or from lower to higher concentration). [1 M]

2. IUPAC of Isopropyl alcohol: Propan-2-ol. [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. F-centers: The electron-trapped anionic vacancies in a crystal lattice which impart color to the crystal. [1 M]

5. Order of a reaction: The sum of the powers of the concentration terms of reactants appearing in the experimentally determined rate law expression. [1 M]

6. Peptide bond: An amide linkage ($-CO-NH-$) formed between the carboxyl group of one $\alpha$-amino acid and the amino group of another with the elimination of water. [1 M]

7. Product of Grignard + Dry Ice: Acetic acid (Ethanoic acid). [1 M]

8. Percentage Atom Economy: (Formula weight of desired product / Sum of formula weights of all reactants) $\times 100$. [1 M]

SECTION B [16 Marks] (Attempt Any 8)

Q3. Ideal vs Non-ideal solutions:

Ideal Solutions	Non-ideal Solutions
Strictly obey Raoult's law at all concentrations.	Do not obey Raoult's law.
$\Delta H_{mix} = 0$ and $\Delta V_{mix} = 0$.	$\Delta H_{mix} \neq 0$ and $\Delta V_{mix} \neq 0$.

[1 M for each point. Total 2 M]

Q4. EAN Calculation for $[Fe(CN)_6]^{4-}$:

Atomic number of Fe ($Z$) = 26. [1/2 M]

Oxidation state ($X$): $x + 6(-1) = -4 \implies x = +2$. [1/2 M]

Electrons from 6 $CN^-$ ligands ($Y$) = $6 \times 2 = 12$. [1/2 M]

EAN = $Z - X + Y = 26 - 2 + 12 = 36$. [1/2 M]

Q5. Reimer-Tiemann Reaction:

Phenol + $CHCl_3 + 3NaOH(aq) \xrightarrow{340 \text{ K}} \text{Intermediate} \xrightarrow{H_3O^+} \text{Salicylaldehyde} + 3NaCl$. [2 M for correct reaction sequence]

Q6. Bromine water on Aniline:

Forms a white precipitate of 2,4,6-tribromoaniline at room temperature. [1 M]

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

Q7. Saytzeff's Rule:

During dehydrohalogenation, the major product is the alkene that is more highly substituted (has more alkyl groups attached to the double bond). [1 M]

Example: 2-bromobutane with alc. KOH gives But-2-ene (80%) as major product and But-1-ene (20%) as minor product. [1 M]

Q8. Monomers of Nylon-6,6:

1. Hexamethylenediamine: $H_2N-(CH_2)_6-NH_2$ [1 M]

2. Adipic acid (Hexanedioic acid): $HOOC-(CH_2)_4-COOH$ [1 M]

Q9. Applications of Nanomaterials:

Used in targeted drug delivery systems in medicine. [1 M]
Silver nanoparticles are used in water purifiers due to antimicrobial properties. [1 M]

Q10. $\Delta H$ 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 $PV_2 = n_2RT$. Substituting: $\Delta H = \Delta U + (n_2 - n_1)RT \implies \Delta H = \Delta U + \Delta n_g RT$. [1 M]

Q11. Cell Constant Numerical:

Given: $R = 100 \text{ }\Omega$, $\kappa = 0.0129 \text{ S/cm}$. [1/2 M]

Formula: Cell Constant ($b$) $= \kappa \times R$ [1/2 M]

Calc: $b = 0.0129 \times 100 = 1.29 \text{ cm}^{-1}$ [1 M]

Q12. Anomalous Properties of Oxygen:

Oxygen is a diatomic gas ($O_2$), others are polyatomic solids (e.g., $S_8$). [1 M]
Oxygen is paramagnetic, others are diamagnetic. (Or: Max covalency is 4 due to absence of d-orbitals). [1 M]

Q13. Salt Bridge:

A U-tube containing a saturated solution of an inert electrolyte (like KCl) in agar-agar gel. [1 M]

Functions: (1) Completes inner electrical circuit. (2) Maintains electrical neutrality in half-cells. [1 M for functions]

Q14. Enantiomers vs Diastereomers:

Enantiomers are non-superimposable mirror images; Diastereomers are not mirror images.
Enantiomers have identical physical properties; Diastereomers have different physical properties.

[1 M for each point. Total 2 M]

SECTION C [24 Marks] (Attempt Any 8)

Q15. $S_N2$ Mechanism:

Single-step concerted process. $CH_3Br + OH^- \rightarrow CH_3OH + Br^-$. [1 M]

Nucleophile $OH^-$ attacks carbon from the backside. Forms an unstable pentacoordinate transition state. [1 M]

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

Q16. 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 M]

Hydrolysis: $C_6H_5C(OOH)(CH_3)_2 \xrightarrow{H^+} C_6H_5OH + CH_3COCH_3$ (Acetone). [1 M]

Preferred commercially because a highly valuable by-product, Acetone, is formed. [1 M]

Q17. First-Order Integrated Rate Law:

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

Integrate from limits $[A]_0$ to $[A]_t$ and 0 to 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]

Q18. Optical Isomerism & $[Co(en)_3]^{3+}$:

Definition: Complexes that are non-superimposable mirror images of each other. [1 M]

Drawing: Show octahedral Co center with three bidentate 'en' ligands and its mirror image (dextro and laevo forms). [2 M for drawing]

Q19. $K_b$ Numerical:

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

$K_b = \frac{M_2 \cdot \Delta T_b \cdot W_1}{1000 \cdot W_2} = \frac{128 \times 0.402 \times 50}{1000 \times 0.5126}$ [1 M]

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

Q20. Gabriel Phthalimide Synthesis:

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

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

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

Q21. Carbohydrates & Classification:

Def: Optically active polyhydroxy aldehydes or ketones. [1 M]

Class based on hydrolysis:

Monosaccharides (cannot be hydrolyzed, e.g., Glucose). [1/2 M]
Oligosaccharides (yield 2-10 units, e.g., Sucrose). [1/2 M]
Polysaccharides (yield >10 units, e.g., Starch). [1 M]

Q22. Preparation of $K_2Cr_2O_7$:

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]

Q23. Catalytic and Magnetic Properties (Transition Metals):

Catalytic: Provide large surface area and variable oxidation states to form unstable intermediate compounds, lowering activation energy. [1.5 M]

Magnetic: Transition metal ions generally have unpaired electrons in d-orbitals. Each unpaired electron acts like a tiny magnet (spin magnetic moment), making the substances paramagnetic. [1.5 M]

Q24. $W_{max}$ Derivation:

$dW = -P_{ex} dV$. Reversible: $P_{ex} = P - dP$. 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]

Q25. $S_N1$ vs $S_N2$ (Any 3 points):

$S_N1$	$S_N2$
Two-step mechanism.	Single-step mechanism.
Carbocation intermediate is formed.	Transition state is formed (no intermediate).
Results in Racemization.	Results in Inversion of configuration.

[1 M for each point. Total 3 M]

Q26. Atom Economy Numerical:

Formula weight of desired product ($C_4H_9Br$) $= 137$. [1 M]

Total weight of all reactants ($C_4H_9OH + NaBr + H_2SO_4$) $= 74 + 103 + 98 = 275$. [1 M]

$\% AE = \frac{137}{275} \times 100 = 49.81\%$. [1 M]

SECTION D [12 Marks] (Attempt Any 3)

Q27. (a) Nernst Eq Numerical [3 Marks] (b) Secondary cell [1 Mark]

(a) $E^\circ_{cell} = 0.34 - (-2.37) = 2.71 \text{ V}$. $n = 2$. [1 M]
$E_{cell} = 2.71 - \frac{0.0592}{2} \log_{10}\left(\frac{0.1}{0.001}\right) = 2.71 - 0.0296 \log_{10}(100)$ [1 M]
$E_{cell} = 2.71 - 0.0592 = 2.6508 \text{ V}$. [1 M]

(b) A cell that can be recharged by passing direct current through it in the reverse direction. [1 M]

Q28. (a) Aldol Condensation [3 Marks] (b) IUPAC of Acetone [1 Mark]

(a) Two molecules of acetaldehyde 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) Propan-2-one. [1 M]

Q29. (a) $t_{1/2}$ Numerical [3 Marks] (b) Pseudo first order [1 Mark]

(a) $t = 40$, $[A]_0 = 100$, $[A]_t = 70$.
$k = \frac{2.303}{40} \log\left(\frac{100}{70}\right) = \frac{2.303 \times 0.1548}{40} = 0.00891 \text{ min}^{-1}$. [2 M]
$t_{1/2} = \frac{0.693}{0.00891} = 77.77 \text{ min}$. [1 M]

(b) A reaction that is expected to be of higher order but follows first-order kinetics due to one reactant being in large excess (e.g., hydrolysis of ester). [1 M]

Q30. (a) Contact Process [3 Marks] (b) Oleum [1 Mark]

(a) 1. $S_8(s) + 8O_2(g) \rightarrow 8SO_2(g)$ [1 M]
2. $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ ($V_2O_5$ 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]

(b) $H_2S_2O_7$. [1 M]

Q31. (a) VBT for $[Ni(CN)_4]^{2-}$ [3 Marks] (b) Coordination Number [1 Mark]

(a) $Ni^{2+}$ is $3d^8$. $CN^-$ is a strong field ligand, forces pairing of the 2 unpaired electrons in 3d. Leaves one inner 3d orbital empty. [1 M]
Uses one 3d, one 4s, and two 4p orbitals $\rightarrow$ $dsp^2$ hybridization $\rightarrow$ Square planar geometry. [1 M]
Since all electrons are paired, it is Diamagnetic. [1 M]

(b) The total number of coordinate bonds formed between ligands and the central metal ion. [1 M]

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