Question

A 90 ml HCl solution of 0.1M is added to 10 mL 0.89 M NaOH solution. To this mixture, 40 mL of H₂SO₄ solution is added to get a pH of 2. The molarity of H₂SO₄ added is –

• A. 0.00812
• B. 0.01625
• C. 0.0325
• D. 0.065

Answer 1

Answer: (B)

0.01625

Answer 2

m. moles of [H⁺] = 90 × 0.1 = 9

m. moles of [OH^–] = 0.89 × 10 = 8.9

Let molarity of H₂SO₄ = M

then m. moles of $\lbrack H^{+}\rbrack_{H_{2}SO_{4} = 40 \times 2M = 80M}$

[H⁺]_resulting = (80M + 9 – 8.9)/140

Ž 0.01 = $\frac{80M + 0.1}{140}$ Ž 1.4 – 0.1 = 80M

Ž 80M = 1.3 Ž M = 0.01625