Question

Calculate the number of molecules of oxalic acid (H₂C₂O₄·2H₂O) in 100 ml of 0.2N oxalic acid solution.

Answer 1

Given: Volume of solution = 100 mL = 0.1 L

Normality (N) = 0.2 N

Formula of oxalic acid = H₂C₂O₄·2H₂O

n-factor of oxalic acid = 2 (because it can donate 2 H⁺ ions)

Avogadro’s number N_A = 6.022 × 10²³

Molarity (M) = `"Normality"/"n-factor"`

= `0.2/2`

= 0.1 mol/L

Moles = Molarity × Volume (L)

= 0.1 × 0.1

= 0.01 mol

Number of molecules = 0.01 × 6.022 × 10²³

= 6.022 × 10²¹

∴ The number of molecules of oxalic acid in 100 ml of 0.2N oxalic acid solution is 6.022 × 10²¹.