NEET Equilibrium — Set 2

Question 1

The $ K_a $ of $ \ce{HNO2} $ is $ 4.5 \times 10^{-4} $. What is the $ K_b $ of $ \ce{NO2-} $ 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}}{4.5 \times 10^{-4}} \approx 2.22 \times 10^{-11} $.

Question 2

For $ \ce{2P(g) <=> Q(g)} $, if $ K_p = 0.1 $ at 500 K ($ R = 0.0831 \, \text{bar L/mol K} $), what is $ K_c $?

Accepted Answer

$ K_p = K_c (RT)^{\Delta n} $, $ \Delta n = 1 - 2 = -1 $, $ RT = 0.0831 \times 500 = 41.55 $. Thus, $ K_c = K_p \times RT = 0.1 \times 41.55 = 4.155 $.

Question 3

In the equilibrium $ \ce{A2(g) <=> 2A(g)} $, if $ K_p = 0.5 $ at 400 K, what happens when the volume is doubled at constant temperature?

Accepted Answer

Decreasing pressure (doubling volume) favors the side with more moles of gas. Here, $ \Delta n = 2 - 1 = 1 $, so the equilibrium shifts to the right (towards $ \ce{A} $).

NEET Chemistry: Equilibrium — Practice Set 2

Q1. The \( K_a \) of \( \ce{HNO2} \) is \( 4.5 \times 10^{-4} \). What is the \( K_b \) of \( \ce{NO2-} \) at 298 K?

Q2. For \( \ce{2P(g) <=> Q(g)} \), if \( K_p = 0.1 \) at 500 K (\( R = 0.0831 \, \text{bar L/mol K} \)), what is \( K_c \)?

Q3. In the equilibrium \( \ce{A2(g) <=> 2A(g)} \), if \( K_p = 0.5 \) at 400 K, what happens when the volume is doubled at constant temperature?

Q4. Which factor does not affect the position of equilibrium in \( \ce{A(g) + B(g) <=> C(g)} \)?

Q5. For \( \ce{2SO3(g) <=> 2SO2(g) + O2(g)} \), \( K_p = 0.01 \) at 900 K. If 1 mole of \( \ce{SO3} \) is placed in a 1 L vessel, what is the partial pressure of \( \ce{O2} \) at equilibrium (\( R = 0.0831 \, \text{bar L/mol K} \))?

Q6. The \( K_{sp} \) of \( \ce{CaCO3} \) is \( 3.8 \times 10^{-9} \). What is its solubility in pure water in mol/L?

Q7. For \( \ce{A(g) <=> 2B(g)} \), \( K_c = 0.16 \) at 400 K. If 0.5 mol \( \ce{A} \) is in a 1 L vessel, what is \( [\ce{B}] \) at equilibrium?

Q8. For \( \ce{2A(g) <=> B(g)} \), \( K_c = 0.25 \) at 500 K. If 0.4 mol \( \ce{A} \) is in a 2 L vessel, what is the degree of dissociation?

Q9. For the reaction \( \ce{PCl5(g) <=> PCl3(g) + Cl2(g)} \), if \( K_p = 1.8 \) at 500 K and \( R = 0.0831 \, \text{bar L/mol K} \), what is \( K_c \)?

Q10. A solution of \( \ce{HA} \) (\( K_a = 1.0 \times 10^{-6} \)) has a pH of 4. What is the concentration of \( \ce{HA} \)?