NEET Equilibrium — Set 8

Question 1

The $ K_a $ of $ \ce{CH3COOH} $ is $ 1.8 \times 10^{-5} $. What is the $ K_b $ of $ \ce{CH3COO-} $ at 298 K?

Accepted Answer

$ K_w = K_a \times K_b = 1.0 \times 10^{-14} $, $ K_b = \frac{1.0 \times 10^{-14}}{1.8 \times 10^{-5}} \approx 5.56 \times 10^{-10} $.

Question 2

For $ \ce{A2(g) <=> 2A(g)} $, $ K_c = 0.09 $ at 300 K. If 0.2 mol $ \ce{A2} $ is in a 1 L vessel, what is the degree of dissociation?

Accepted Answer

Initial: $ [\ce{A2}] = 0.2 \, \text{M} $. Let $ \alpha $ be the degree of dissociation, $ [\ce{A2}] = 0.2 (1 - \alpha) $, $ [\ce{A}] = 0.4\alpha $. $ K_c = \frac{[\ce{A}]^2}{[\ce{A2}]} = \frac{(0.4\alpha)^2}{0.2 (1 - \alpha)} = 0.09 $, $ 0.8\alpha^2 = 0.09 (1 - \alpha) $, $ \alpha \approx 0.3 $.

Question 3

What is the pH of a solution containing 0.01 M $ \ce{HCl} $ assuming complete dissociation?

Accepted Answer

For $ \ce{HCl} $, $ [\ce{H+}] = 0.01 \, \text{M} = 10^{-2} \, \text{M} $, so $ \text{pH} = -\log(10^{-2}) = 2 $.

NEET Chemistry: Equilibrium — Practice Set 8

Q1. The \( K_a \) of \( \ce{CH3COOH} \) is \( 1.8 \times 10^{-5} \). What is the \( K_b \) of \( \ce{CH3COO-} \) at 298 K?

Q2. For \( \ce{A2(g) <=> 2A(g)} \), \( K_c = 0.09 \) at 300 K. If 0.2 mol \( \ce{A2} \) is in a 1 L vessel, what is the degree of dissociation?

Q3. What is the pH of a solution containing 0.01 M \( \ce{HCl} \) assuming complete dissociation?

Q4. In a saturated solution of a sparingly soluble salt \( \ce{MX2} \), the solubility is \( S \) mol/L. If \( K_{sp} = 4S^3 \), what is the relationship between \( \ce{M^{2+}} \) and \( \ce{X^-} \)?

Q5. For the reaction \( \ce{2A(g) + B(g) <=> 3C(g)} \), \( K_c = 64 \) at 300 K. If 2 moles of \( \ce{A} \) and 1 mole of \( \ce{B} \) are placed in a 2 L vessel, what is \( [\ce{C}] \) at equilibrium?

Q6. Which of the following is a Lewis base?

Q7. For \( \ce{2A(g) <=> B(g) + C(g)} \), \( K_c = 0.0625 \) at 300 K. If 0.8 mol \( \ce{A} \) is placed in a 2 L vessel with 0.1 mol \( \ce{B} \), what is \( [\ce{C}] \) at equilibrium?

Q8. For the reaction \( \ce{2A(g) + 2B(g) <=> 3C(g)} \), \( K_c = 64 \) at 500 K. If 2 moles of \( \ce{A} \) and 2 moles of \( \ce{B} \) are placed in a 1 L vessel, what is \( [\ce{C}] \) at equilibrium?

Q9. A weak acid \( \ce{HX} \) (\( K_a = 3.2 \times 10^{-5} \)) is mixed with 0.04 M \( \ce{NaX} \) in a 2:1 volume ratio (acid:salt). If \( [\ce{HX}] = 0.06 \, \text{M} \) after mixing, what is the pH?

Q10. A weak base \( \ce{BOH} \) (\( K_b = 5.0 \times 10^{-6} \)) has a 0.1 M solution with \( \alpha = 0.00707 \). What is the pH?