(a) hydrocyanic acid Ka 4 92 x 10-10. pKa
(b) acetic acid Ka pKa 4.75
(c) lactic acid Ka 8.40 x 104 pKa
(d) formic acid. KapKa 3.75
(e) Which of these acids is the strongest?
Answer:
(a) pKa = -logKa = – Log(4.92 * 10-10) = 9.31
(b) Ka = 10-pKa = 10-4.75 = 1.78 * 10-5
(c) pKa = – Log(8.40 * 10-4) = 3.08
(d) Ka = 10-pKa = 10-3.75 = 1.78 * 10-4
(e) The acid with higher Ka or lower pKa is strongest.
So, (c)