Butanoic acid, which contributes to the rancid odor of spoiled butter, is a weak monoprotic acid with Ka=1.80×10−5 mol dm−3K_{\text{a}} = 1.80 \times 10^{-5}\text{ mol dm}^{-3}Ka=1.80×10−5 mol dm−3 at 298 K.
What is the concentration, in mol dm−3\text{mol dm}^{-3}mol dm−3, of hydrogen ions in a 2.00 × 10-2 mol dm-3 aqueous solution of butanoic acid at 298 K?
3.60×10−73.60 \times 10^{-7}3.60×10−7
6.00×10−46.00 \times 10^{-4}6.00×10−4
1.20×10−31.20 \times 10^{-3}1.20×10−3
3.00×10−23.00 \times 10^{-2}3.00×10−2
