In: Chemistry
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