A Buffer Solution with a PH of 4

Multiple Choice

A buffer solution with a pH of 4.78 is prepared with ________ M formic acid and 0.90 M sodium formate. The K_a of formic acid is 1.8 × 10^-4.

A) 0.083
B) 0.17
C) 3.3 × 10³
D) 9.8
E) 0.041