Question

Art a the ph of a 0. 25 m aqueous solution of hydrofluoric acid, hf, at 25. 0 °c is 2. 3. What is the value of ka for hf

Answer 1

The value of $K_{a}$ for HF is, 3.5 x $10^{-4} M$

What is an aqueous solution?

The aqueous solution definition means simply that something has been dissolved in water. The aqueous symbol is (aq). Aqueous solution definition: something is dissolved in water.

Solution : Given,

pH = 2.03

Concentration of HF = 0.25 M

First, we have to calculate the concentration of $H^{+}$ ion.

pH=-log [$H^{+}$]

2.03=-log [$H^{+}$]

$H^{+}$= 9.3 x $10^{-3} M$

Now we have to calculate the value of  $K_{a}$ for HF.

The equilibrium reaction will be:

$HF\leftrightharpoons \ H^{+}+F^{-}$

Concentration of  $H^{+}$ = Concentration of  $F^{-}$= 9.3 x $10^{-3} M$

The expression of $K_{a}$ for HF will be,

$k_{a} =\frac{[F]^{-} [H]^{+} }{HF}$

$K_{a}$ = 3.5 x $10^{-4} M$

Therefore, the value of $K_{a}$ for HF is, 3.5 x $10^{-4} M$

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