JEE Main 2023 · 25 January · morning · Single correct · +4 / −1

'25 volume' hydrogen peroxide means

  1. (a) 1 L marketed solution contains 75 g of H₂O₂.
  2. (b) 1 L marketed solution contains 250 g of H₂O₂.
  3. (c) 1 L marketed solution contains 25 g of H₂O₂.
  4. (d) 100 mL marketed solution contains 25 g of H₂O₂.
Answer and solution

Answer (a) 1 L marketed solution contains 75 g of H₂O₂.

Solution

Chemistry ma’am · 4 steps

Volume strength counts litres of oxygen, not grams, so turn those litres back into grams of H₂O₂.

  1. What volume means. 25 volume means 1 L of the solution gives 25 L of O₂ at STP when it decomposes. The number counts litres of oxygen gas, not grams of H₂O₂.

    2H₂O₂ → 2H₂O + O₂

  2. Use the equation. Two moles of H₂O₂ (2 × 34 = 68 g) give one mole of O₂, which is 22.4 L at STP.
  3. Scale to 25 L. Mass of H₂O₂ needed = (68 × 25)/22.4 = 75.9 g. With 22.7 L as the molar volume you get 74.9 g. Either way it is about 75 g in 1 L.
  4. So. 1 L of '25 volume' H₂O₂ holds about 75 g of H₂O₂, which is option (a).

The idea to keep. Volume strength is litres of O₂ at STP from 1 L of solution. Molarity is volume strength divided by 11.2, and grams per litre is that molarity times 34.

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

Study Hydrogen & s-Block Elements

Asked about 130 times in JEE Main since 2020. This question is from 2023.