A volumetric analysis

Question

1.A 0.4040g sample of potassium hydrogen phthalatte, KHC8H4O4(molar mass=204.44g/mol) is dissolved wwith 50ml of deionized water in a 125ml Erlenmeyer flask. the sample is titrated to the phenolphthalein endpoint with 14.71ml of a sodium hydroxied solution. what is the molar concentration of the NaOH solution?

2.A 25ml aliquot of a nitric acid solution of unknown concentration is pipetted into a 125ml Erlenmeyer flask and drops of phenolphthalein are added. the above sodium hydroxide solution(the titrant) is used to titrate the nitric acid solution(the analyte). if 18.92ml of the titrant is dispensed from a buret in causing a color change of the phenolphthalein, what is the molar concentration of the nitric acid solution?

Answer 1

1.

KHC8H4O4 + NaOH ---->  KNaC8H4O4 + H2O

1 mol of acid reacts with 1 mol of base.

0.4040 g acid x (1 mol / 204.44 g) = 0.001976 mol acid

0.001976 mol acid x (1 mol base / 1 mol acid) = 0.001976 mol NaOH

M = mol / L = 0.001976 mol / 0.01471 L = 0.1343 M NaOH

2.

HNO3 + NaOH ---->  NaNO3 + H2O

1 mol of acid reacts with 1 mol of base.

M = mol / L

mol = M x L = 0.1343 mol/L x 0.01892 L = 0.002542 mol NaOH

0.002542 mol NaOH x (1 mol HNO3 / 1 mol NaOH) = 0.002542 mol HNO3

M = mol / L = 0.002542 mol / 0.02500 L = 0.1017 M HNO3