A 0.10 M weak acid HA with $p K_{a} = 5.0$ is titrated with 0.10 M NaOH. Which statements are correct? ( $lo g 9 = 0.954$ .)

Answer: A, B, D

At 50% neutralisation pH

= p K_{a} = 5.0

. At equivalence the salt NaA hydrolyses, so pH

> 7

. Methyl orange changes colour far below the equivalence pH and is unsuitable. At 90%: pH

= 5.0 + lo g 9 = 5.95

. Answer A, B, D.

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