Question

What is the ph of a solution of 0.20 m hno2 containing 0.10 m nano2 at 25°c

Answer 1

This is an incomplete question, here is a complete question.

What is the pH of a solution of 0.20 M HNO₂ containing 0.10 M NaNO₂ at 25°C, given Ka of HNO₂ is 4.5 × 10⁻⁴?

Answer : The pH of the solution is, 3.05

Explanation : Given,

`K_a` for HNO₂ = 4.5 × 10⁻⁴

Concentration of
`HNO_2` = 0.20 M

Concentration of
`NaNO_2` = 0.10 M

First we have to calculate the value of
`pK_a`.

The expression used for the calculation of
`pK_a` is,

`pK_a=-\log (K_a)`

Now put the value of
`K_a` in this expression, we get:

`pK_a=-\log (4.5* 10^(-4))`

`pK_a=4-\log (4.5)`

`pK_a=3.35`

Now we have to calculate the pH of the solution.

Using Henderson Hesselbach equation :

`pH=pK_a+\log ([Salt])/([Acid])`

`pH=pK_a+\log ([NaNO_2])/([HNO_2])`

Now put all the given values in this expression, we get:

`pH=3.35+\log (((0.10))/(0.20))`

`pH=3.05`

Therefore, the pH of the solution is, 3.05