🧪 Chemical Equilibrium — Practice Worksheet

Q1. For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), the expression for Kc is:

1. [NH₃]² / ([N₂][H₂]³)
2. [N₂][H₂]³ / [NH₃]²
3. [NH₃] / ([N₂][H₂])
4. 2[NH₃] / ([N₂] + 3[H₂])

Q2. The relationship between Kp and Kc is Kp = Kc(RT)^Δn. For the reaction PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), Δn is:

1. 0
2. 1
3. −1
4. 2

Q3. According to Le Chatelier's principle, increasing pressure on the equilibrium N₂ + 3H₂ ⇌ 2NH₃ will:

1. Shift equilibrium to the left
2. Shift equilibrium to the right
3. Have no effect
4. Decrease the value of Kc

Q4. A catalyst in a reversible reaction:

1. Increases the equilibrium constant
2. Shifts equilibrium to the right
3. Helps attain equilibrium faster without changing K
4. Increases the yield of products

Q5. The pH of a 0.01 M HCl solution is:

1. 1
2. 2
3. 3
4. 0.01

Q6. The ionic product of water (Kw) at 25°C is:

1. 10⁻⁷
2. 10⁻¹⁴
3. 10⁻¹⁰
4. 10⁻²

Q7. For an endothermic reaction at equilibrium, increasing temperature will:

1. Decrease Kc
2. Increase Kc
3. Not change Kc
4. Make the reaction irreversible

Q8. The solubility product (Ksp) of AgCl is 1.8 × 10⁻¹⁰. The molar solubility of AgCl in pure water is approximately:

1. 1.34 × 10⁻⁵ M
2. 1.8 × 10⁻¹⁰ M
3. 1.8 × 10⁻⁵ M
4. 9 × 10⁻⁶ M

Q9. The conjugate base of H₂PO₄⁻ is:

1. H₃PO₄
2. HPO₄²⁻
3. PO₄³⁻
4. H₂PO₄⁻

Q10. A buffer solution can be prepared by mixing:

1. Strong acid + strong base
2. Weak acid + its conjugate base (salt)
3. Strong acid + weak acid
4. Two strong bases

Q11. If the reaction quotient Q > K for a reaction, the reaction will:

1. Proceed in the forward direction
2. Proceed in the backward direction
3. Be at equilibrium
4. Stop completely

Q12. The degree of dissociation of a weak acid increases with:

1. Increase in concentration
2. Decrease in concentration (dilution)
3. Addition of a strong acid
4. Decrease in temperature

Q13. For the equilibrium 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), the units of Kp are:

1. atm
2. atm⁻¹
3. atm²
4. No units

Q14. The Henderson-Hasselbalch equation for an acidic buffer is:

1. pH = pKa + log([acid]/[salt])
2. pH = pKa + log([salt]/[acid])
3. pH = pKb + log([salt]/[base])
4. pH = pKw − pKa

Q15. The common ion effect causes the solubility of a sparingly soluble salt to:

1. Increase
2. Decrease
3. Remain unchanged
4. Become zero

Q16. For the reaction H₂(g) + I₂(g) ⇌ 2HI(g), Kc = 54.3 at 698 K. If [H₂] = [I₂] = 0.5 M at equilibrium, find [HI].

Q17. Calculate the pH of a 0.1 M acetic acid solution (Ka = 1.8 × 10⁻⁵).

Q18. The Ksp of PbCl₂ is 1.7 × 10⁻⁵. Calculate its molar solubility in pure water.

Q19. A buffer is prepared by mixing 0.2 M CH₃COOH and 0.3 M CH₃COONa. Calculate the pH (pKa of acetic acid = 4.76).

Q20. At a certain temperature, Kc for the reaction 2NO₂(g) ⇌ N₂O₄(g) is 4.0. If the initial concentration of NO₂ is 0.2 M, find the equilibrium concentrations of both species.

Q21. Calculate the pH of a solution obtained by mixing 50 mL of 0.1 M NaOH and 50 mL of 0.05 M H₂SO₄.

Q22. The degree of dissociation of 0.1 M acetic acid is 1.34%. Calculate Ka and the pH of the solution.

Q23. For the reaction N₂O₄(g) ⇌ 2NO₂(g), Kp = 0.98 atm at 25°C. Calculate Kc (R = 0.0821 L·atm/mol·K).

Q24. Will a precipitate of BaSO₄ form when 100 mL of 0.001 M BaCl₂ is mixed with 100 mL of 0.0001 M Na₂SO₄? (Ksp of BaSO₄ = 1.1 × 10⁻¹⁰)

Q25. The solubility of Ca(OH)₂ in water is 0.013 M. Calculate the Ksp and the pH of a saturated Ca(OH)₂ solution.