Answer : The pH of the solution is, 1.88
Explanation : Given,

Concentration of
= 0.35 M
Concentration of
= 0.29 M
First we have to calculate the value of
.
The expression used for the calculation of
is,
![pK_a=-\log [K_a]](https://tex.z-dn.net/?f=pK_a%3D-%5Clog%20%5BK_a%5D)
Now put the value of
in this expression, we get:



Now we have to calculate the pH of the solution.
Using Henderson Hesselbach equation :
![pH=pK_a+\log \frac{[Salt]}{[Acid]}](https://tex.z-dn.net/?f=pH%3DpK_a%2B%5Clog%20%5Cfrac%7B%5BSalt%5D%7D%7B%5BAcid%5D%7D)
![pH=pK_a+\log \frac{[NaClO_2]}{[HClO_2]}](https://tex.z-dn.net/?f=pH%3DpK_a%2B%5Clog%20%5Cfrac%7B%5BNaClO_2%5D%7D%7B%5BHClO_2%5D%7D)
Now put all the given values in this expression, we get:


Therefore, the pH of the solution is, 1.88