Chemistry · EQUILIBRIUM

An aqueous buffer solution contains 0.25 M \( \text{NH}_4\text{Cl} \) and 0.10 M \( \text{NH}_3 \). If the dissociation constant of ammonia is \( K_b = 1.80 \times 10^{-5} \) and \( K_w = 1.0 \times 10^{-14} \), the hydrogen ion concentration \( [\text{H}^+] \) in the solution is:

1. A
   \( 1.39 \times 10^{-9}\text{ M} \)
2. B
   \( 7.20 \times 10^{-6}\text{ M} \)
3. C
   \( 2.78 \times 10^{-9}\text{ M} \)
4. D
   \( 5.56 \times 10^{-10}\text{ M} \)