Respuesta :
Answer : The pH of the solution is, 4.0
Explanation : Given,
Acid dissociation constant for formic acid, [tex]K_a=1.8\times 10^{-4}[/tex]
Concentration of formic acid (acid) = 0.120 M
Concentration of sodium formate (salt) = 0.240 M
First we have to calculate the value of [tex]pK_a[/tex].
The expression used for the calculation of [tex]pK_a[/tex] is,
[tex]pK_a=-\log (K_a)[/tex]
Now put the value of [tex]K_a[/tex] in this expression, we get:
[tex]pK_a=-\log (1.8\times 10^{-4})[/tex]
[tex]pK_a=4-\log (1.8)[/tex]
[tex]pK_a=3.7[/tex]
Now we have to calculate the pH of buffer.
Using Henderson Hesselbach equation :
[tex]pH=pK_a+\log \frac{[Salt]}{[Acid]}[/tex]
Now put all the given values in this expression, we get:
[tex]pH=3.7+\log (\frac{0.240}{0.120})[/tex]
[tex]pH=4.0[/tex]
Thus, the pH of the solution is, 4.0
The pH of the solution is 4.0.
Calculation of the ph of the solution;
Since the acid dissociation constant for formic acid is 1.8*10^-4
Concentration of formic acid (acid) = 0.120 M
And,
Concentration of sodium formate (salt) = 0.240 M
Now first determine the pKa i.e.
= -log(ka)
= -log(1.8*10^*-4)
= 3.7
Now the pH should be
= 3.7 + log(0.240/0.120)
= 4.0
hence, The pH of the solution is 4.0.
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