Answer: The ratio of [tex]\frac{[A^-]}{[HA]}[/tex] is 0.1
Explanation:
The chemical equation for the dissociation of monoprotic weak acid (formic acid) follows:
[tex]HA\rightleftharpoons H^++A^-[/tex]
To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:
[tex]pH=pK_a+\log(\frac{[salt]}{[acid]})[/tex]
[tex]pH=pK_a+\log(\frac{[A^-]}{[HA]})[/tex]
We are given:
[tex]pK_a[/tex] = negative logarithm of acid dissociation constant of methanoic acid = 3.75
[tex]\frac{[A^-]}{[HA]}[/tex] = ratio of concentration of salt and acid
pH = 2.75
Putting values in above equation, we get:
[tex]2.75=3.75+\log(\frac{[A^-]}{[HA]})\\\\\frac{[A^-]}{[HA]}=0.1[/tex]
Hence, the ratio of [tex]\frac{[A^-]}{[HA]}[/tex] is 0.1
