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Stoichiometry 3: Mass-to-MassIntroductionPreviously, we learned how to convert from moles of a product or reactant in a chemical reaction to mass (grams) of another substance. Consider the following example of heating phosphorus in the presence of oxygen: P4(s) + 5O2(g) → 2P2O5(s)If we weigh out exactly 25.0g of phosphorus, we can predict the moles of diphosphorus pentaoxide that will be produced as a result. First, we set up a grams-to-moles conversion for the phosphorus using its molar mass. The molar mass of P4 is (31g x 4 = 124g)25.0g of P4 x 1 mole P4124g P4 Next, we need to add a conversion factor to convert from P4 to P2O5 based on the coefficients from the reaction.25.0g of P4 x 1 mole P4124.0g P4 x 2 moles P2O5 1 mole P4 This tells us the moles of P2O5, but we actually want to know mass. One more conversion factor must be added using the molar mass of P2O5. The molar mass of P2O5 is (31g x 2) + (16g x 5) = 142g.25.0g of P4 x 1 mole P4124.0g P4 x 2 moles P2O5 1 mole P4 x 142g P2O5 1 moles P2O5 = 57.3g P2O5ExampleFirst, balance this double displacement equation between Lead (II) nitrate and sodium chloride.:__Pb(NO3)2(aq) + __NaCl(aq) → __PbCl2(s) + __NaNO3(aq)Then, answer the following questions with a conversion factor:How many grams of lead (II) chloride would be produced by reacting 50.0g of sodium chloride?How many grams of lead (II) nitrate would be needed to produce 81.0g of sodium nitrate?PracticeSulfur dioxide gas decomposes into solid sulfur (S8) and oxygen gas. How many grams of solid sulfur would be produced from 25.0g of sulfur dioxide?Equation: ________________________________________________The answer will be in: ______________________________________Conversion Factor:Solid potassium oxide and aqueous sulfuric acid react to produce solid potassium sulfate and liquid water. How many grams of sulfuric acid would be needed to fully react with 32.5g of potassium oxide?Equation: ________________________________________________The answer will be in: ______________________________________Conversion Factor:Solid iron (III) reacts with silver (I) chloride to produce iron (III) chloride and solid silver. What mass of silver chloride would you need to produce exactly 85.0g of solid silver?Equation: ________________________________________________The answer will be in: ______________________________________Conversion Factor:Hydrogen gas and oxygen gas can react to form liquid water. If exactly 33.5g of water vapor was produced from lighting a balloon filled with hydrogen gas, what was the original mass of the hydrogen?Equation: ________________________________________________The answer will be in: ______________________________________Conversion Factor:Butane (C4H10) is burned in the presence of oxygen gas to produce water vapor and carbon dioxide gas. What is the minimum mass of oxygen that must be present to fully react 100.0g of butane?Equation: ________________________________________________The answer will be in: ______________________________________Conversion Factor: ................
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