A buffer contains 0.30 M of a weak acid HA (K_a = 1.8 x 10^-5) and 0.15 M of NaA. Find [H+] in units of 10^-5 M, to one decimal place.

JEE Main levelNumerical answerDifficulty 2 of 3ie141

A buffer contains 0.30 M of a weak acid HA ( $K_{a} = 1.8 \times 1 0^{- 5}$ ) and 0.15 M of NaA. Find $[H X^{+}]$ in units of $1 0^{- 5} M$ , to one decimal place.

Numerical answer type, answer in x 10^-5 M, tolerance 0.05.

[H X^{+}] = K_{a} [HA] / [A^{-}] = 1.8 \times 1 0^{- 5} \times 0.30/0.15 = 3.6 \times 1 0^{- 5} M