The Foundations of Chemistry

The concentration of unreacted HCl in the total volume of 120. mL is

MHCl0.067 MHCl

[H 3 O]6.7 10 
^2 M so pH1.17

3.After 50.0 mL of 0.100 MNaOH has been added (midpoint of the titration):

HCl  NaOH 88n NaCl H 2 O

start 10.0 mmol 5.0 mmol 0 mmol

change 
5.0 mmol 
5.0 mmol 5.0 mmol

after rxn 5.0 mmol 0 mmol 5.0 mmol

MHCl0.033 MHCl

[H 3 O]3.3 10 
^2 M so pH1.48

4.After 100. mL of 0.100 MNaOH has been added:

HCl  NaOH 88n NaCl H 2 O

start 10.0 mmol 10.0 mmol 0 mmol

change 
10.0 mmol 
10.0 mmol 10.0 mmol

after rxn 0 mmol 0 mmol 10.0 mmol

We have added enough NaOH to neutralize the HCl exactly so this is the equiva-

lence point. A strong acid and a strong base react to give a neutral salt solution so

pH7.00.

5.After 110.0 mL of 0.100 MNaOH has been added:

HCl  NaOH 88n NaCl H 2 O

start 10.0 mmol 11.0 mmol 0 mmol

change 
10.0 mmol 
10.0 mmol 10.0 mmol

after rxn 0 mmol 1.0 mmol 10.0 mmol

The pH is determined by the excess NaOH.

5.00 mmol HCl



150. mL

8.00 mmol HCl



120. mL

19-5 Strong Acid/Strong Base Titration Curves 811

Some household products. Each

solution contains a few drops of a

universal indicator. A color of yellow

or red indicates a pH less than 7. A

green to purple color indicates a pH

greater than 7.

The end point of the titration of 0.100 MHCl with 0.100 MNaOH using another
indicator, bromthymol blue.