Question

Part 1. We’re going to titrate formic acid with the strong base, NaOH. There is initially 100. mL of 0.50 M formic acid and the concentration of NaOH is 1.0 M. All work must be shown to receive credit.

If, instead of NaOH being added, 0.05 moles of HCl is added by bubbling the gas through the solution. Assume that the volume has not changed. What is the percent dissociation of formic acid?

Answer 1

0.05 moles of HCl is added to 100. mL of 0.50 M formic acid

Initial concentration (M)	0.50	0.50 (from HCl)	0
Change in concentration (M)	-x	x	x
Equilibrium concentration (M)	0.50-x	0.50+x	x

The acid dissociation constant for HCOOH is 0.00018

Since the value of Ka is small, we approximate 0.50-x to 0.50.

This is quadratic equation with solution

or

The value is discarded as formic acid is weak acid so x should be small.

Hence,

The percent dissociation of formic acid in presence of 0.05 moles of HCl is