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A pyrotechnician mixes 280 g of black powder for a firework. Find the amount of oxygen, carbon dioxide, and sulfur dioxide generated when this firework bursts, if the oxidizing agent in the powder is saltpeter. Which are the limiting reactants for each reaction? Based on this, calculate the maximum yield of oxygen, carbon dioxide, and sulfur dioxide when 280 g of black powder is burned. When the pyrotechnician tested the firework, he found the actual yields of oxygen, carbon dioxide, and sulfur dioxide to be 81.57 g, 82.75 g, and 46.5 g respectively. What is the percent yield of each gas? Why should pyrotechnicians worry about the yield of the reactants in a firework? How does the yield affect the firework and the environment?

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MissPhiladelphia
Supposing the given percentages are percents by mass: 
(280 g) x (0.10) / (32.0655 g S/mol) x (1 mol SO2 / 1 mol S) x (64.0638 g SO2/mol) = 55.9 g SO2 
(280 g) x (0.10) / (32.0655 g S/mol) x (1 mol O2 / 1 mol S) x (31.99886 g O2/mol) = 27.9 g O2 reacted with S 
(280 g) x (0.15) / (12.01078 g C/mol) x (1 mol CO2 / 1 mol C) x (44.00964 g CO2/mol) = 154 g CO2 
(280 g) x (0.15) / (12.01078 g C/mol) x (1 mol O2 / 1 mol C) x (31.99886 g O2/mol) = 112 g O2 reacted with C 
Supposing the amount of O2 asked about is the amount left over after reacting with the S and C: 
(280 g) x (0.75) / (101.10332 g KNO3/mol) x (5 mol O2 / 4 mol KNO3) x (31.99886 g O2/mol) = 83.1 g O2 total produced by KNO3 

So there is not enough oxygen in the KNO3 to react with all the C and S present, so the questions still can't be answered, since clearly some of the C and S are being oxidized by an unknown amount of atmospheric oxygen.

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