A solution of hydrochloric acid of unknown concentration was titrated with 0.10 M NaOH. If a 100.-mL sample of the HCl solution required exactly 1.0 mL of the NaOH solution to reach the equivalence point, what was the initial pH of the HCl solution? g

The Ph is 3

Explanation:

First of all, calculate the concentration of the acid.

The balanced equation of reaction is:

HCl + NaOH ===> NaCl + H2O

Using titration equation of formula

CAVA/CBVB = NA/NB

Where NA is the number of mole of acid = 1 (from the balanced equation of reaction)

NB is the number of mole of base = 1 (from the balanced equation of reaction)

CA is the concentration of acid = ?

CB is the concentration of base = 0.1M

VA is the volume of acid = 100 mL

VB is the volume of base = 1mL

Substituting

CA×100/0.1×1 = 1/1

Therefore CA =0.1×1×1/100×1

CA = 0.001 M (this is the hydrogen ion concentration)

Ph of the acid is calculated using

Ph = -log [H+]

= -log 0.001

= 3