NEET Equilibrium — Set 15

Question 1

A weak acid $ \ce{HX} $ ($ K_a = 1.0 \times 10^{-4} $) has a 0.1 M solution mixed with 0.05 M $ \ce{NaX} $ in a 1:2 volume ratio. What is the pH?

Accepted Answer

Total volume = 3V, $ [\ce{HX}] = \frac{0.1V}{3V} = 0.0333 \, \text{M} $, $ [\ce{X-}] = \frac{0.05 \times 2V}{3V} = 0.0333 \, \text{M} $, $ \text{pH} = 4 + \log \frac{0.0333}{0.0333} = 4 $.

Question 2

For $ \ce{A(g) + 2B(g) <=> 2C(g)} $, $ K_p = 0.25 $ at 400 K. If the total pressure at equilibrium is 4 atm and $ P_{\ce{A}} = 1 \, \text{atm} $, what is $ P_{\ce{C}} $?

Accepted Answer

Total pressure = $ P_{\ce{A}} + P_{\ce{B}} + P_{\ce{C}} = 4 $, $ P_{\ce{B}} + P_{\ce{C}} = 3 $. $ K_p = \frac{(P_{\ce{C}})^2}{P_{\ce{A}} (P_{\ce{B}})^2} = \frac{(P_{\ce{C}})^2}{1 \cdot (3 - P_{\ce{C}})^2} = 0.25 $, $ P_{\ce{C}} = 0.5 (3 - P_{\ce{C}}) $, $ P_{\ce{C}} = 1.5 - 0.5 P_{\ce{C}} $, $ 1.5 P_{\ce{C}} = 1.5 $, $ P_{\ce{C}} = 1 \, \text{atm} $.

Question 3

For the equilibrium $ \ce{CO(g) + H2O(g) <=> CO2(g) + H2(g)} $, if the initial concentrations of $ \ce{CO} $ and $ \ce{H2O} $ are 0.2 M each and at equilibrium $ [\ce{CO2}] = 0.08 \, \text{M} $, what is $ K_c $?

Accepted Answer

At equilibrium, $ [\ce{CO}] = [\ce{H2O}] = 0.2 - 0.08 = 0.12 \, \text{M} $, $ [\ce{CO2}] = [\ce{H2}] = 0.08 \, \text{M} $. Thus, $ K_c = \frac{[\ce{CO2}][\ce{H2}]}{[\ce{CO}][\ce{H2O}]} = \frac{(0.08)^2}{(0.12)^2} = \frac{0.0064}{0.0144} \approx 0.444 $.

NEET Chemistry: Equilibrium — Practice Set 15

Q1. A weak acid \( \ce{HX} \) (\( K_a = 1.0 \times 10^{-4} \)) has a 0.1 M solution mixed with 0.05 M \( \ce{NaX} \) in a 1:2 volume ratio. What is the pH?

Q2. For \( \ce{A(g) + 2B(g) <=> 2C(g)} \), \( K_p = 0.25 \) at 400 K. If the total pressure at equilibrium is 4 atm and \( P_{\ce{A}} = 1 \, \text{atm} \), what is \( P_{\ce{C}} \)?

Q3. For the equilibrium \( \ce{CO(g) + H2O(g) <=> CO2(g) + H2(g)} \), if the initial concentrations of \( \ce{CO} \) and \( \ce{H2O} \) are 0.2 M each and at equilibrium \( [\ce{CO2}] = 0.08 \, \text{M} \), what is \( K_c \)?

Q4. In \( \ce{2A(g) + B(g) <=> 2C(g)} \), if \( K_c = 4 \) and the equilibrium mixture contains 0.2 mol \( \ce{A} \), 0.1 mol \( \ce{B} \), and 0.4 mol \( \ce{C} \) in a 1 L vessel, what happens if 0.1 mol \( \ce{A} \) is added?

Q5. The \( K_a \) of \( \ce{HF} \) is \( 6.8 \times 10^{-4} \). What is the \( K_b \) of \( \ce{F-} \) at 298 K?

Q6. For \( \ce{CO(g) + Cl2(g) <=> COCl2(g)} \), \( K_c = 25 \) at 500 K. If 0.2 mol \( \ce{CO} \) and 0.3 mol \( \ce{Cl2} \) are in a 1 L vessel, what is \( [\ce{COCl2}] \) at equilibrium?

Q7. In \( \ce{A(g) + 2B(g) <=> 2C(g)} \), \( K_c = 2 \) and \( [\ce{A}] = 0.2 \, \text{M} \), \( [\ce{B}] = 0.4 \, \text{M} \), \( [\ce{C}] = 0.4 \, \text{M} \) at equilibrium. What happens if \( \ce{C} \) is added?

Q8. For \( \ce{2NO(g) <=> N2(g) + O2(g)} \), \( K_c = 0.01 \) at 300 K. If 0.4 mol \( \ce{NO} \) and 0.1 mol \( \ce{N2} \) are in a 2 L vessel, what is \( [\ce{O2}] \) at equilibrium?

Q9. The solubility of \( \ce{PbI2} \) in 0.05 M \( \ce{KI} \) is \( 1.0 \times 10^{-4} \, \text{M} \). What is its \( K_{sp} \)?

Q10. A weak acid \( \ce{HX} \) (\( K_a = 4.0 \times 10^{-6} \)) is mixed with 0.03 M \( \ce{NaX} \) in a 2:1 volume ratio (acid:salt). If \( [\ce{HX}] = 0.08 \, \text{M} \) after mixing, what is the pH?