NEET Equilibrium — Set 7

Question 1

For the equilibrium $ \ce{2A(g) <=> B(g) + C(g)} $, if $ K_c = 0.04 $ and $ [\ce{A}] = 0.4 \, \text{M} $ at equilibrium, what is $ [\ce{B}] $?

Accepted Answer

$ K_c = \frac{[\ce{B}][\ce{C}]}{[\ce{A}]^2} = 0.04 $, $ [\ce{B}] = [\ce{C}] = x $, $ 0.04 = \frac{x^2}{(0.4)^2} = \frac{x^2}{0.16} $, $ x^2 = 0.0064 $, $ x = 0.08 \, \text{M} $.

Question 2

A weak base $ \ce{NH3} $ ($ K_b = 1.8 \times 10^{-5} $) is mixed with 0.02 M $ \ce{NH4Cl} $ in a 1:1 volume ratio. If the final $ [\ce{NH3}] = 0.05 \, \text{M} $, what is the pH?

Accepted Answer

$ [\ce{NH4+}] = 0.01 \, \text{M} $, $ \text{p}K_b = 4.74 $, $ \text{pOH} = 4.74 + \log \frac{0.01}{0.05} = 4.74 - 0.7 = 4.04 $, $ \text{pH} = 14 - 4.04 = 9.96 $.

Question 3

A weak base $ \ce{NH3} $ ($ K_b = 1.8 \times 10^{-5} $) is 1% ionized in a solution. What is $ [\ce{NH3}] $?

Accepted Answer

Let $ [\ce{NH3}] = C $, $ \alpha = 0.01 $, $ [\ce{OH-}] = C \alpha = 0.01C $. $ K_b = \frac{(0.01C)^2}{C(1 - 0.01)} \approx \frac{0.0001C^2}{0.99C} = 1.01 \times 10^{-4}C = 1.8 \times 10^{-5} $, $ C = \frac{1.8 \times 10^{-5}}{1.01 \times 10^{-4}} \approx 0.178 \, \text{M} $.

NEET Chemistry: Equilibrium — Practice Set 7

Q1. For the equilibrium \( \ce{2A(g) <=> B(g) + C(g)} \), if \( K_c = 0.04 \) and \( [\ce{A}] = 0.4 \, \text{M} \) at equilibrium, what is \( [\ce{B}] \)?

Q2. A weak base \( \ce{NH3} \) (\( K_b = 1.8 \times 10^{-5} \)) is mixed with 0.02 M \( \ce{NH4Cl} \) in a 1:1 volume ratio. If the final \( [\ce{NH3}] = 0.05 \, \text{M} \), what is the pH?

Q3. A weak base \( \ce{NH3} \) (\( K_b = 1.8 \times 10^{-5} \)) is 1% ionized in a solution. What is \( [\ce{NH3}] \)?

Q4. A weak acid \( \ce{HX} \) (\( K_a = 1.0 \times 10^{-5} \)) and its salt \( \ce{NaX} \) are mixed in equal volumes of 0.2 M and 0.1 M solutions, respectively. What is the pH?

Q5. A weak acid \( \ce{HY} \) (\( K_a = 1.0 \times 10^{-5} \)) has a 0.2 M solution mixed with 0.1 M \( \ce{NaY} \) in a 1:1 volume ratio. What is the pH?

Q6. For \( \ce{A(g) + B(g) <=> 2C(g)} \), \( K_p = 4 \) at 300 K. If the total pressure at equilibrium is 3 atm and \( P_{\ce{A}} = P_{\ce{B}} \), what is \( P_{\ce{C}} \)?

Q7. For \( \ce{CH4(g) + H2O(g) <=> CO(g) + 3H2(g)} \), \( K_c = 0.1 \) at 800 K. If 0.5 mol \( \ce{CH4} \) and 0.5 mol \( \ce{H2O} \) are in a 2 L vessel, what is \( [\ce{H2}] \) at equilibrium?

Q8. A 0.05 M solution of a weak base \( \ce{B} \) has a pH of 10. What is its \( K_b \)?

Q9. For \( \ce{Ag2CrO4(s) <=> 2Ag+(aq) + CrO4^{2-}(aq)} \), \( K_{sp} = 1.1 \times 10^{-12} \). In a 0.005 M \( \ce{AgNO3} \) solution, what is \( [\ce{CrO4^{2-}}] \) in a saturated solution?

Q10. A solution has a pH of 2.5. What is \( [\ce{H+}] \) in mol/L?