The hydrogen ion concentration in weak acid o | vedclass

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Question

Given- $K_a$ and $c$

To find $-\left[H^{+}\right]=$?

$\quad\quad\quad\quad HA \rightleftharpoons H ^{+}+ A ^{-}$

$t=0 \quad\quad c \quad\quad

Vedclass · Accepted Answer

$\sqrt {{K_a}c} $

Vedclass · Answer

Given- $K_a$ and $c$

To find $-\left[H^{+}ight]=$?

$\quad\quad\quad\quad HA ightleftharpoons H ^{+}+ A ^{-}$

$t=0 \quad\quad c \quad\quad\quad0\quad \quad 0$

$t=t_1 \quad c-x \quad\quad x \quad\quad x$

For very weak acid $\Rightarrow x\,<<<,1$

$K_a =\frac{\left[H^{+}ight]\left[A^{-}ight]}{[H A]}$

$=\frac{x 	imes x}{c-x}$

where,$K_a =	ext { Dissociation censtent }$

$c =[H A]$

$x =H^{+} 	ext {concentration }$

As $\quad x\,<<<\,1$ so $c-x \approx c$

$	herefore k_a =\frac{x^2}{c}$

$\Rightarrow x=\sqrt{k_a C}$

The hydrogen ion concentration in weak acid of dissociation constant ${K_a}$ and concentration $c$ is nearly equal to

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