1. Check if the equation is balanced, luckily this one is! 2. Check if any unit conversions are needed. All masses are in grams, so no problem there. 3. Using (moles = mass ÷ Mr), calculate: the no. of moles of SO₂ (44.3 ÷ 64.1 = 0.69); and the no. of moles of H₂S (44.3 ÷ 34.1 = 1.30). This is to work out which reagent is in excess. 4. As there is a molar ratio of 1:2, you can divide the latter answer by 2 to get the expected no. of moles of SO₂ (0.65). Therefore, SO₂ is in excess. 5. Use (mass = moles x Mr) to find out the mass of sulfur (0.65 x 32.1 x 3 = 62.6g). Remember to multiply by 3 to get the correct mass as you need to consider the molar ratios.