Question

What is standardization in acid-base chemistry? What constitutes a standsrd in analytical chemistry? Give types & examples.

Answer 1

Method 1 : Standardisation of NaOH using KHP
A 0.128 g sample of KHP (HKC8H4O4) required 28.54 mL of NaOH solution to reach a phenolphthalein endpoint. Calculate the molarity of the NaOH.
HKC8H4O4 + NaOH -----> NaKC8H4O4 + H2O
(0.128 g KHP)(1 mol / 204.23 g KHP ) = 6.267 x 10-4 mol KHP
(6.267 x 10-4 mol KHP)(1 mol NaOH / 1 mol KHP) = 6.267 x 10-4 mol NaOH
6.267 x 10-4 mol NaOH / 0.02854 L NaOH = 0.0220 M NaOH

Method 2 : Standardisation of HCl using NaOH
A 20.00 mL sample of HCl was titrated with the NaOH solution from method1. To reach the endpoint required 23.72 mL of the NaOH. Calculate the molarity of the HCl.
HCl + NaOH -----> NaCl + H2O
(0.02372 L NaOH)(0.0220 mol NaOH / 1 L NaOH) = 5.218 x 10-4 mol NaOH
(5.218 x 10-4 mol NaOH)(1 mol HCl / 1 mol NaOH) = 5.218 x 10-4 mol HCl
5.218 x 10-4 mol HCl / 0.02000 L HCl = 0.0261 M HCl