The PH of a 0

Multiple Choice

The pH of a 0.0338 M solution of a weak acid is 2.85. What is K _a of this acid?

A) 3.4×10 ^{- 2}
B) 1.4×10 ^{- 3}
C) 3.4×10 ^{- 4}
D) 6.2×10 ^{- 5}
E) 5.9×10 ^{- 5}