NEET Equilibrium — Set 12

Question 1

For $ \ce{A(g) + 2B(g) <=> 2C(g)} $, if $ K_c = 4 $ and $ [\ce{C}] = 0.8 \, \text{M} $, $ [\ce{B}] = 0.4 \, \text{M} $ at equilibrium, what is $ [\ce{A}] $?

Accepted Answer

$ K_c = \frac{[\ce{C}]^2}{[\ce{A}][\ce{B}]^2} = 4 $, $ 4 = \frac{(0.8)^2}{[\ce{A}](0.4)^2} = \frac{0.64}{[\ce{A}] \times 0.16} $, $ 4 \times 0.16 [\ce{A}] = 0.64 $, $ 0.64 [\ce{A}] = 0.64 $, $ [\ce{A}] = 1.0 \, \text{M} $.

Question 2

A weak base $ \ce{BOH} $ ($ K_b = 2.0 \times 10^{-5} $) has a 0.1 M solution with pH 10.5. What is the degree of ionization?

Accepted Answer

$ \text{pOH} = 14 - 10.5 = 3.5 $, $ [\ce{OH-}] = 10^{-3.5} \approx 3.16 \times 10^{-4} $, $ \alpha = \frac{[\ce{OH-}]}{[\ce{BOH}]} = \frac{3.16 \times 10^{-4}}{0.1} = 3.16 \times 10^{-3} = 0.00316 $.

Question 3

A weak base $ \ce{BOH} $ has $ K_b = 4.0 \times 10^{-4} $. If its 0.02 M solution has a pH of 10.8, what is the percentage ionization?

Accepted Answer

$ \text{pH} = 10.8 $, $ \text{pOH} = 14 - 10.8 = 3.2 $, $ [\ce{OH-}] = 10^{-3.2} \approx 6.31 \times 10^{-4} $. $ [\ce{BOH}] = 0.02 - 6.31 \times 10^{-4} \approx 0.0194 $. $ K_b = \frac{[\ce{OH-}]^2}{[\ce{BOH}]} = \frac{(6.31 \times 10^{-4})^2}{0.0194} \approx 2.05 \times 10^{-5} $, but given $ K_b = 4.0 \times 10^{-4} $, ionization $ \alpha = \frac{[\ce{OH-}]}{[\ce{BOH}]_{\text{initial}}} = \frac{6.31 \times 10^{-4}}{0.02} = 0.03155 $, % = 3.155%.

NEET Chemistry: Equilibrium — Practice Set 12

Q1. For \( \ce{A(g) + 2B(g) <=> 2C(g)} \), if \( K_c = 4 \) and \( [\ce{C}] = 0.8 \, \text{M} \), \( [\ce{B}] = 0.4 \, \text{M} \) at equilibrium, what is \( [\ce{A}] \)?

Q2. A weak base \( \ce{BOH} \) (\( K_b = 2.0 \times 10^{-5} \)) has a 0.1 M solution with pH 10.5. What is the degree of ionization?

Q3. A weak base \( \ce{BOH} \) has \( K_b = 4.0 \times 10^{-4} \). If its 0.02 M solution has a pH of 10.8, what is the percentage ionization?

Q4. A weak acid \( \ce{HB} \) (\( K_a = 1.0 \times 10^{-6} \)) is mixed with 0.03 M \( \ce{NaOH} \) in a 3:1 volume ratio (acid:base). If the final \( [\ce{HB}] = 0.08 \, \text{M} \), what is the pH?

Q5. Which species acts as a Lewis acid?

Q6. For \( \ce{2A(g) <=> B(g)} \), \( K_c = 0.04 \) at 300 K. If 0.5 mol \( \ce{A} \) is in a 1 L vessel, what is \( [\ce{B}] \) at equilibrium?

Q7. For \( \ce{A(g) + B(g) <=> 2C(g)} \), \( K_p = 1 \) at 300 K. If the total pressure at equilibrium is 3 atm and \( P_{\ce{A}} = 1 \, \text{atm} \), what is \( P_{\ce{C}} \)?

Q8. The solubility of \( \ce{BaSO4} \) in 0.05 M \( \ce{Na2SO4} \) is \( 2.0 \times 10^{-9} \, \text{M} \). What is its \( K_{sp} \)?

Q9. The \( K_{sp} \) of \( \ce{Mg(OH)2} \) is \( 1.8 \times 10^{-11} \). What is the pH at which \( [\ce{Mg^{2+}}] = 1.0 \times 10^{-4} \, \text{M} \) in a saturated solution?

Q10. For \( \ce{XY(s) <=> X+(aq) + Y-(aq)} \), if \( K_{sp} = 9.0 \times 10^{-6} \), what is \( [\ce{X+}] \) in mol/L?