What Combination of Substances Will Give a Buffered Solution That

Multiple Choice

What combination of substances will give a buffered solution that has a pH of 5.05? Assume each pair of substances is dissolved in 5.0 L of water. (K_b for NH₃ = 1.8  10^-5; K_b for C₅H₅N = 1.7  10^-9)

A) 1.0 mol C₅H₅N and 1.5 mol C₅H₅NHCl
B) 1.0 mol NH₃ and 1.5 mol NH₄Cl
C) 1.5 mol NH₃ and 1.0 mol NH₄Cl
D) 1.5 mol C₅H₅N and 1.0 mol C₅H₅NHCl
E) none of these