NEET Equilibrium — Set 19

Question 1

For $ \ce{HA <=> H+ + A-} $, if $ K_a = 1.0 \times 10^{-5} $ and $ [\ce{HA}] = 0.05 \, \text{M} $ at equilibrium, what is $ [\ce{H+}] $?

Accepted Answer

$ K_a = \frac{[\ce{H+}][\ce{A-}]}{[\ce{HA}]} = \frac{x^2}{0.05 - x} \approx \frac{x^2}{0.05} = 1.0 \times 10^{-5} $, $ x^2 = 5.0 \times 10^{-7} $, $ x = 7.07 \times 10^{-4} \, \text{M} $.

Question 2

For $ \ce{2X(g) <=> Y(g)} $, if $ K_p = 0.25 $ at 300 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 300 = 24.93 $. Thus, $ K_c = K_p \times RT = 0.25 \times 24.93 \approx 6.23 $.

Question 3

Which of the following is a Bronsted-Lowry acid?

Accepted Answer

A Bronsted-Lowry acid donates a proton. $ \ce{HCO3-} $ can donate $ \ce{H+} $ to form $ \ce{CO3^{2-}} $.

NEET Chemistry: Equilibrium — Practice Set 19

Q1. For \( \ce{HA <=> H+ + A-} \), if \( K_a = 1.0 \times 10^{-5} \) and \( [\ce{HA}] = 0.05 \, \text{M} \) at equilibrium, what is \( [\ce{H+}] \)?

Q2. For \( \ce{2X(g) <=> Y(g)} \), if \( K_p = 0.25 \) at 300 K (\( R = 0.0831 \, \text{bar L/mol K} \)), what is \( K_c \)?

Q3. Which of the following is a Bronsted-Lowry acid?

Q4. For the reaction \( \ce{H2(g) + I2(g) <=> 2HI(g)} \), the equilibrium concentrations are \( [\ce{H2}] = 0.02 \, \text{M} \), \( [\ce{I2}] = 0.02 \, \text{M} \), and \( [\ce{HI}] = 0.16 \, \text{M} \). What is the value of the equilibrium constant \( K_c \)?

Q5. For \( \ce{N2(g) + 3H2(g) <=> 2NH3(g)} \), \( K_p = 4.0 \times 10^{-3} \) at 600 K. If 1 mole of \( \ce{N2} \) and 3 moles of \( \ce{H2} \) are in a 2 L vessel, what is \( P_{\ce{NH3}} \) at equilibrium (\( R = 0.0831 \, \text{bar L/mol K} \))?

Q6. A weak acid \( \ce{HX} \) (\( K_a = 2.0 \times 10^{-5} \)) is mixed with 0.06 M \( \ce{NaX} \) in a 1:2 volume ratio (acid:salt). If \( [\ce{HX}] = 0.04 \, \text{M} \) after mixing, what is the pH?

Q7. A weak acid \( \ce{HY} \) (\( K_a = 1.0 \times 10^{-4} \)) is mixed with its salt \( \ce{NaY} \) in a 2:1 molar ratio. If \( [\ce{HY}] = 0.2 \, \text{M} \), what is the pH?

Q8. For the reaction \( \ce{X(g) + Y(g) <=> 2Z(g)} \), if \( K_c = 25 \) and at equilibrium \( [\ce{Z}] = 0.5 \, \text{M} \), what is \( [\ce{X}] \) if \( [\ce{Y}] = 0.02 \, \text{M} \)?

Q9. For \( \ce{2A(g) <=> B(g) + C(g)} \), \( K_p = 0.5 \) at 600 K. If the initial pressure of \( \ce{A} \) is 2 atm, what is \( P_{\ce{B}} \) at equilibrium?

Q10. In a physical equilibrium \( \ce{H2O(l) <=> H2O(g)} \), what happens if the temperature is increased?