Chemistry MCQ Practice 27 — Science Foundation Course for Class 11 & 12

1. A solution of 0.1 M urea shows osmotic pressure of 2.46 atm at 300 K. The value of R used here is:

(a) 0.0821 L atm K⁻¹ mol⁻¹ (b) 0.821 L atm K⁻¹ mol⁻¹ (c) 8.314 J K⁻¹ mol⁻¹ (d) 1.987 cal K⁻¹ mol⁻¹

Show Answer & Explanation

Correct Answer: (a) 0.0821 L atm K⁻¹ mol⁻¹

Explanation:
π = CRT → 2.46 = 0.1 × R × 300 → R = 0.082

2. The number of unpaired electrons in [Mn(H₂O)₆]²⁺ is:

(a) 3 (b) 4 (c) 5 (d) 1

Show Answer & Explanation

Correct Answer: (c) 5

Explanation:
Mn²⁺ is d⁵ high spin (weak field water ligand)

3. Which of the following is a biodegradable polymer used in packaging?

(a) Polythene (b) PVC (c) PHBV (d) Teflon

Show Answer & Explanation

Correct Answer: (c) PHBV

Explanation:
Poly-β-hydroxybutyrate-co-β-hydroxyvalerate is biodegradable

4. The vitamin whose deficiency causes pellagra is:

(a) Vitamin B₁ (b) Vitamin B₂ (c) Vitamin B₃ (Niacin) (d) Vitamin B₁₂

Show Answer & Explanation

Correct Answer: (c) Vitamin B₃ (Niacin)

Explanation:
Niacin deficiency causes pellagra (3 Ds: dermatitis, diarrhoea, dementia)

5. The IUPAC name of the compound CH₃-CH₂-C(CH₃)₂-CH₂-CH₃ is:

(a) 3,3-Dimethylpentane (b) 2,2-Dimethylpentane (c) 3-Methylhexane (d) 2-Methylhexane

Show Answer & Explanation

Correct Answer: (a) 3,3-Dimethylpentane

Explanation:
Longest chain of 5 carbons with two methyl groups at position 3

6. The correct order of bond dissociation energy is:

(a) Cl₂ > Br₂ > F₂ > I₂ (b) F₂ > Cl₂ > Br₂ > I₂ (c) I₂ > Br₂ > Cl₂ > F₂ (d) Br₂ > Cl₂ > F₂ > I₂

Show Answer & Explanation

Correct Answer: (a) Cl₂ > Br₂ > F₂ > I₂

Explanation:
Cl₂ has the highest bond energy

7. The activation energy of a reaction can be determined from:

(a) Arrhenius equation (b) Rate law (c) Integrated rate equation (d) Order of reaction

Show Answer & Explanation

Correct Answer: (a) Arrhenius equation

Explanation:
ln k = ln A - Ea/RT (plot of ln k vs 1/T gives slope = -Ea/R)

8. The flux used in the smelting of copper ore is:

(a) Limestone (b) Silica (c) Coke (d) Sodium carbonate

Show Answer & Explanation

Correct Answer: (b) Silica

Explanation:
Silica removes FeO as slag (FeSiO₃)

9. The polymer used in making contact lenses is:

(a) Perspex (b) Silicone (c) Teflon (d) Nylon

Show Answer & Explanation

Correct Answer: (a) Perspex

Explanation:
Polymethyl methacrylate (PMMA) is used for contact lenses

10. The enzyme that hydrolyses urea is:

(a) Urease (b) Amylase (c) Pepsin (d) Lipase

Show Answer & Explanation

Correct Answer: (a) Urease

Explanation:
Urease catalyses the hydrolysis of urea to ammonia and CO₂