H3A is a weak tribasic acid with Ka1 = 10−5, Ka2 = 10−9 and Ka3 = 10−13. The value of pX of 0.1 M –

Question

H3A is a weak tribasic acid with Ka1 = 10−5, Ka2 = 10−9 and Ka3 = 10−13. The value of pX of 0.1 M – H3A solution, where pX = −log10X and X = $\frac{\left\lbrack A^{3 -} \right\rbrack}{\left\lbrack HA^{2 -} \right\rbrack}$, is

Accepted Answer

$\left\lbrack H^{+} ightbrack = \sqrt{0.1 	imes 10^{- 5}} = 10^{- 3}	ext{ M}$Now, $K_{a_{3}} = \frac{\left\lbrack H^{+} ightbrack\left\lbrack A^{3 -} ightbrack}{\left\lbrack HA^{2 -} ightbrack} \Rightarrow \frac{\left\lbrack A^{3 -} ightbrack}{\left\lbrack HA^{2 -} ightbrack} = \frac{10^{- 13}}{10^{- 3}} = 10^{- 10}$$	herefore P^{x} = 10$

Question

Options

Solution

More Ionic Equilibrium Questions