Question

The specific gravity of h2so4 is 1.8g/cc and this solution is found to contain 98% h2so4 by weight.10cc of this solution is mixed with 350cc of pure water.25ml of this dil h2so4 solution neutralises 500ml of naoh solution. Then pH of solution is

Answer 1

Given:

• Specific gravity of H₂SO₄ (d) = 1.8 g/cc
• Mass % of H₂SO₄ = 98%
• Volume of H₂SO₄ taken (V1) = 10 cc
• Volume of pure water (V2) = 350 cc
• Volume of acid used in neutralization (Va) = 25 mL
• Volume of NaOH solution (Vb) = 500 mL
• Molar mass of H₂SO₄ = 98 g/mol

To find:

The pH of the NaOH solution.

Solution:

• Total volume of H₂SO₄ solution on mixing with water = 10 + 350 = 360mL
• Mass of H₂SO₄ present in the H₂SO₄ solution = d*V1*98/100
• Moles of H₂SO₄ present in the solution = (d*V1*98/100)/98 = 0.18
• Moles of H₂SO₄ present in 25 mL of the solution = 0.18*25/360 = 0.0125
• Moles of NaOH = 2* moles of H₂SO₄ used for neutralization = 0.025
• Concentration of NaOH solution (M) = 0.025*1000/ 500 = 0.05 M
• pH of the NaOH solution = 14 - (-log(M)) = 14 + log(0.05) = 12.699

Answer:

The pH of the NaOH solution = 12.699