A buffer solution is prepared in which the concentration of $NH_3$ is 0.30 M and the concentration of $NH_4^+$ is 0.20 M. If the equilibrium constant, $K_b$ for $NH_3$ equals $1.8 × 10^{–5}$, what is the pH of this solution? ($\log 2.7 = 0.43$)

Question

( A ) 9.08
( B ) 9.43
( C ) 11.72
( D ) 8.73