Some Basic Concepts of Chemistry

If 50 mL of 0.5 M oxalic acid is required to neutralise 25 mL of NaOH solution, the amount of NaOH in 50 mL of given NaOH solution is g.

Answer

4

Solution

H2C2O4 + 2NaOH Na2C2O4 + 2H2O

mmol of oxalic acid = 50 × 0.5 = 25 ⇒ mmol of NaOH = 2 × 25 = 50 (in 25 mL)

⇒ MNaOH = 5025 = 2 M

∴ NaOH in 50 mL = 2 × 50 = 100 mmol = 0.1 mol = 0.1 × 40 = 4 g

Answer: 4