An Ammonia Buffer Contains NH₃:NH₄⁺ in a Ratio of 0

Multiple Choice

An ammonia buffer contains NH₃:NH₄⁺ in a ratio of 0.4 moles:0.6 moles (pK = 9.75) . What will be the pH if you add 0.01 moles of HCl to this buffer?

A) 8.98
B) 9.04
C) 9.25
D) 9.46
E) 9.52