Answer to Question #307824 in Physical Chemistry for Abbs

Question

A Laboratory assistant prepares 5 litres of 0.1N hydrochloric acid stock solution

using commercial HCl available in laboratory which has percentage purity of 35%

(w/w) and specific gravity of 1.18 g/ml. Then he fills five 100ml standard flasks with

50.0ml of 0.1N HCl solution and dilutes it with distilled water upto the mark. Then he

takes 10ml of diluted HCl solution from each flask into a conical flask, mixes it and

adds 50ml of 0.025M Sodium hydroxide solution to it. Finally, he adds few drops of

phenolphthalein to the resulting solution in the conical flask.

i) What was the concentration of HCl solution prepared in 100ml standard

flasks?

ii) What do you think will be the colour of the resulting solution after addition of

indicator?

iii) Calculate the pH of the resulting solution.

Answer 1

i. Mole= Concentration×Volume

0.1 = concentration× 100

= 0.001M

ii. white

iii. pH of 8