Answer to Question #187245 in General Chemistry for Shannen

Question

A 15.00 g sample containing mixed alkali and other inert components was dissolved and diluted to 300 mL with water. A 20 mL aliquot was titrated with 5.02 mL of 0.5352 M HCl to reach PHP endpoint. Another 20 mL aliquot was titrated to the BCG endpoint, using up 18.87 mL of titrant in the process. 

Answer 1

Let's find the concentration of alkali used for both PHP and BCG endpoint

For the PHP endpoint

Volume of alkali V1= 20ml

Concentration of Alkali C1= ?

Volume of acid V2= 5.02ml

Concentration of acid C2= 0.5352M

C1V1=C2V2

C1= C2V2/V1

= 0.5352x5.00/20= 0.1338M

For the BCG endpoint

Volume of alkali V1= 20ml

Concentration of Alkali C1= ?

Volume of acid V2= 18.87ml

Concentration of acid C2= 0.5352M

C1= C2V2/V1

= 0.5352 x 18.87/20

= 0.505M