Spectroscopic data show that in a solution of the weak acid

CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases

Problem

HA

, about 90\% of the acid is present as

HA

and 10\% as

A^-

. Which statement best describes the relationship between the solution pH and the acid’s

pK_a

? (a)

\text{pH} \approx pK_a + 1

(b)

\text{pH} \approx pK_a

(c)

\text{pH} \approx pK_a - 1

(d)

\text{pH} \approx pK_a - 2