Question

What is [h3o ] in a solution of 0.25 m ch3co2h and 0.030 m nach3co2?

Answer 1

Hello!

To determine [H₃O⁺], we need to apply the Henderson-Hasselback equation, since this is a case of an acid and its conjugate base:

$pH=pKa+log( \frac{[A^{-}] }{[HA]} )$

$pH=4,76+log( \frac{0,030M}{0,25M} ) \\ \\ pH=3,84$

Now, we use the definition of pH and clear [H₃O⁺] from there:

$pH=-log[H_3O^{+}]$

$[H_3O^{+}] = 10^{-pH} =10^{-3,84}=0,00014 M$

So, the [H₃O⁺] concentration is 0,00014 M

Have a nice day!