In the reaction (SO₂ + 2H₂S → 3S + 2H₂O), 44.3g of SO₂ are mixed with 44.3g of H₂S. Calculate the maximum mass of sulfur that could be formed.
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.
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