The ionization constant of a certain weak acid is `10^(-4)`. What should be the [salt] to [acid] ratio if we have to prepare a buffer with `pH = 5` using this acid and one of the salts

Options

A. `1:10`
B. `10:1`
C. `5:4`
D. `4:5`

Answer

B

Explanation

`pH = - log K_(b) + log. (["salt"])/(["acid"])`
` 5 = - log 10^(-4) + log . (["salt"])/(["acid"])`
`log . (["salt"])/(["acid"]) = 1 `
` (["salt"])/(["acid"])="antilog" 1 = 10 : 1 `