The volume strength of 8.9 M H₂O₂ solution calculated at 273 K and 1 atm is ______. (R = 0.0821 L atm K⁻¹ mol⁻¹) (rounded off ot the nearest integer)

Solution

Chemistry ma’am · 4 steps

Volume strength is the litres of O₂ that 1 L of solution releases, so start from the decomposition.

1. What it means. Volume strength is the volume of O₂, at 273 K and 1 atm, given off when 1 L of H₂O₂ solution decomposes completely.

   2H₂O₂ → 2H₂O + O₂

2. Moles of oxygen. 1 L of 8.9 M solution holds 8.9 mol of H₂O₂. Two moles of H₂O₂ give one mole of O₂, so you get 8.9/2 = 4.45 mol of O₂.
3. Convert to volume. V = nRT/P = (4.45 × 0.0821 × 273)/1 = 4.45 × 22.41 = 99.74 L.
4. So. 1 L of the solution releases about 99.74 L of O₂, so the volume strength is 100.

The common slip: 199. Skipping the 2 : 1 ratio and taking 8.9 mol of O₂ gives about 199, double the right value.

The idea to keep. At 273 K and 1 atm, volume strength = 11.2 × molarity, because 2 mol of H₂O₂ give only 1 mol of O₂, which occupies 22.4 L.

Answer from the NTA final answer key. Solution by PrepWiser.