K _b for Ammonia Is 1

Multiple Choice

K _b for ammonia is 1.8×10 ^{- 5}. Calculate K _a for the ammonium ion.

A) 5.6×10⁴
B) 4.2×10 ^{- 3}
C) 1.8×10 ^{- 5}
D) 1.0×10 ^{- 7}
E) 5.6×10 ^{- 10}