[H^+] = 10^(-PH)

[H^+]of PH = 3 HF solution = 10^-3 mol/L

HF is a weak acid and its dissociation in water is a partial reaction.

`HF harr H^++F^-`

So it is clear that [H^+] is not equal to the initial [HF] because of partial dissociation.

We...

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[H^+] = 10^(-PH)

[H^+]of PH = 3 HF solution = 10^-3 mol/L

HF is a weak acid and its dissociation in water is a partial reaction.

`HF harr H^++F^-`

So it is clear that [H^+] is not equal to the initial [HF] because of partial dissociation.

We need the dissociation constant to get the actual amount of [H^+] of a 4.0 mol/L HF solution. It is clear that the [H^+] will be lower than 4 mol/L. But we cannot say whether it is greater or equal or lower than 10^-3 mol/L as found by PH.

* So we cannot directly say this solution is diluted or concentrated.*