Calculating the Composition of Oleum

To calculate the composition of oleum in terms of its equivalent sulfuric acid concentration, you can use the following steps:

1. First, understand that 100% oleum means 100 grams of SO₃ in the solution.
2. When 100 grams of SO₃ reacts with water, it forms 180 grams of H₂SO₄ (since the molar mass of SO₃ is 80 and that of H₂SO₄ is 98).
3. So, 100% oleum is equivalent to 180 grams of H₂SO₄ in 100 grams of the solution.
4. For example, if you have 20% oleum, it means you have 20 grams of SO₃ in 100 grams of the solution. This 20 grams of SO₃ would form 36 grams of H₂SO₄ (since 20 grams of SO₃ forms (20/80) * 98 grams of H₂SO₄).
5. Therefore, 20% oleum is equivalent to 136 grams of H₂SO₄ in 100 grams of the solution (100 grams original H₂SO₄ + 36 grams formed).