Answer to Question #225157 in Chemistry for Junior

Question

A solution of Ba(OH)2 was standardized against 0.1016 g of primary standard 

benzoic acid C6H5COOH. Calculate the concentration of Ba(OH)2 if the end point 

was 20.89 mL. 

Answer 1

Solution:

The titration reaction is given by the following chemical equation:

Ba(OH)₂ + 2C₆H₅COOH → Ba(C₆H₅COO)₂ + 2H₂O

According to the equation above:

Moles of Ba(OH)₂ = (Moles of C₆H₅COOH) / 2

The molar mass of C₆H₅COOH is 122.12 g/mol.

Therefore,

(0.1016 g C₆H₅COOH) × (1 mol C₆H₅COOH / 122.12 g C₆H₅COOH) = 0.000832 mol C₆H₅COOH

Moles of Ba(OH)₂ = (Moles of C₆H₅COOH) / 2 = (0.000832 mol) / 2 = 0.000416 mol Ba(OH)₂

Molarity = Moles / Solution volume

Molarity of Ba(OH)₂ = (0.000416 mol) / (20.89×10^-3 L) = 0.0199 mol/L = 0.0199 M

Molarity of Ba(OH)₂ = 0.0199 M

Answer: The concentration of Ba(OH)₂ is 0.0199 mol/L