Mass of NaOH = Moles x Mr = 0.2 x 40 = 8g If only 1.7g is obtained what is the % yield? 1.7 / 8 = 21% What mass of calcium oxide could be made from 75 tonnes of limestone (CaCO3)? CaCO3 CaO + CO2 CaCO3 CaO Mass 75 ? Mr 100 56 Moles 0.75 Mass of CaO = Moles x Mr = 0.75 x 56 = 42 tonnes If 17 tonnes are produced, what is the % yield? 17 / 42 = 40% 97.5 g of zinc was added to excess dilute hydrochloric acid: Zn + 2HCl ZnCl2 + H2 Calculate: the mass of zinc chloride that could be produced Zn ZnCl2 H2 Mass 97.5 a b Mr 65 136 2 Moles 1.5 Mass of ZnCl2 = Moles x Mr = 1.5 x 136 = 204g the mass of hydrogen that could be produced. Mass of H2 = Moles x Mr = 1.5 x 2 = 3g A yield of 53% was obtained. What mass of zinc chloride was this? 204 x 0.53 = 108g Part 2: Atom Economy The atom economy of a reaction is the percentage of your reactant that is converted to useful product. This is important for sustainability and economics. We use the formula: Example: extraction of copper: There are two possible ways to extract pure copper metal 2CuO + C → 2Cu + CO2 CuS + O2 → Cu + SO2 We can calculate the atom economy for the first reaction as below: For the second reaction: Showing that the second reaction has a lower atom economy. There are other factors to consider as well, including the usefulness of other products, the % yield of the reaction, the rate and the position of equilibrium. Iron is extracted from iron oxide in the Blast Furnace: Fe2O3 + 3 CO → 2 Fe + 3 CO2 Calculate the maximum theoretical mass of iron that can be made from 100g of iron oxide. Fe2O3 2 Fe
Mass of NaOH = Moles x Mr = 0.2 x 40 = 8g If only 1.7g is obtained what is the % yield? 1.7 / 8 = 21% What mass of calcium oxide could be made from 75 tonnes of limestone (CaCO3)? CaCO3 CaO + CO2 CaCO3 CaO Mass 75 ? Mr 100 56 Moles 0.75 Mass of CaO = Moles x Mr = 0.75 x 56 = 42 tonnes If 17 tonnes are produced, what is the % yield? 17 / 42 = 40% 97.5 g of zinc was added to excess dilute hydrochloric acid: Zn + 2HCl ZnCl2 + H2 Calculate: the mass of zinc chloride that could be produced Zn ZnCl2 H2 Mass 97.5 a b Mr 65 136 2 Moles 1.5 Mass of ZnCl2 = Moles x Mr = 1.5 x 136 = 204g the mass of hydrogen that could be produced. Mass of H2 = Moles x Mr = 1.5 x 2 = 3g A yield of 53% was obtained. What mass of zinc chloride was this? 204 x 0.53 = 108g Part 2: Atom Economy The atom economy of a reaction is the percentage of your reactant that is converted to useful product. This is important for sustainability and economics. We use the formula: Example: extraction of copper: There are two possible ways to extract pure copper metal 2CuO + C → 2Cu + CO2 CuS + O2 → Cu + SO2 We can calculate the atom economy for the first reaction as below: For the second reaction: Showing that the second reaction has a lower atom economy. There are other factors to consider as well, including the usefulness of other products, the % yield of the reaction, the rate and the position of equilibrium. Iron is extracted from iron oxide in the Blast Furnace: Fe2O3 + 3 CO → 2 Fe + 3 CO2 Calculate the maximum theoretical mass of iron that can be made from 100g of iron oxide. Fe2O3 2 Fe
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