Ans.
Molarity of acetic acid (HC2H3O2) = 0.45M
Volume of acetic acid = 500.0 mL
No. of mol of acetic acid is
The equation to calculate pH is given by
where HA = weak acid/acetic acid
A- = conjugate base/acetate ion
For the pH to be equal to the pKa, the no. of mol o the weak acid and that of the conjugate base must be equal.
The reaction of acetic acid and hydroxide ion is
To produce x no. of mol of acetate ion, x no. of mol of the hydroxide ion has to be added. And, it should be equal to the no. of mol of acetic acid.
Therefore, no. of mol of KOH to be added = 0.225 mol
Molar mass of KOH = 56.11g/mol
Therefore, 12.6g of KOH must be added.
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