A solution is prepared by dissolving I .96g of H2SO4 in 250 cm3 of its solution. What is the concentration in moles per dm3?

Analyze the question: A mass of H₂SO₄ is dissolved to make 250 cm³ of solution, and we need the concentration in mol/dm³. The mass is written as "I .96g", which is most likely a typo for 1.96 g.

Concept:

• Moles = mass ÷ molar mass
• Concentration (mol/dm³) = moles ÷ volume in dm³
• 1000 cm³ = 1 dm³, so 250 cm³ = 0.25 dm³

Solution:

1. Molar mass of H₂SO₄ = (2 × 1) + 32 + (4 × 16) = 2 + 32 + 64 = 98 g/mol

2. Moles = 1.96 ÷ 98 = 0.02 mol

3. Volume = 250 ÷ 1000 = 0.25 dm³

4. Concentration = 0.02 ÷ 0.25 = 0.08 mol/dm³

Check with the other reading: If the mass were 19.6 g, the answer would be 0.8 mol/dm³ (option D). But "I .96" fits 1.96 g much better, and that gives B.

Tip: Always convert cm³ to dm³ by dividing by 1000. A quick shortcut is concentration = (mass ÷ molar mass) × (1000 ÷ volume in cm³). Here that is 0.02 × 4 = 0.08.