Question

What is the pH of a buffer that is 0.6 M HF and 0.2 M NaF? The Ka of HF is 6.8 Ã 10â4. What is the pH of a buffer that is:_______ a. 3.65b. 3.17c. 3.50d. 2.69

Answer 1

The correct option is d

Explanation:

From the question we are told that

The concentration of HF is [HF] = 0.6 M

The concentration of NaF is
`[NaF ] = 0.2 M`

The Ka of HF is
`K_a = 6.8 *10^(-4) \`

Generally HF(Hydrogen fluoride ) is ionized as follows

`HF_((aq)) + H_2 O _((l)) \rightleftharpoons H_3O^+ _((aq) ) + F^- _((aq))`

Generally NaF(Sodium fluoride ) is ionized as follows

`NaF_((aq)) + H_2 O _((l)) \rightleftharpoons Na^+ _((aq) ) + F^- _((aq))`

Generally the from Henderson-Hasselbalch equation the pH of the buffer is mathematically represented as

`pH = pKa + log [([NaF ])/(HF) ]`

=>
`pH = -log(K_a) + log [([NaF ])/(HF) ]`

=>
`pH = -log(6.8 *10^(-4)) + log [([0.2 ])/(0.6) ]`

=>
`pH = 2.69`