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Gas Stoichiometry. A balanced equation shows the ratio of moles being used and produced Because of Avogrado’s principle, it also shows the ratio of volumes being used and produced. Example. 2C 4 H 10(g) + 13O 2(g) 8CO 2(g) + 10 H 2 O (g) Shows molar and volume ratios Questions:
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Gas Stoichiometry • A balanced equation shows the ratio of moles being used and produced • Because of Avogrado’s principle, it also shows the ratio of volumes being used and produced
Example 2C4H10(g) + 13O2(g) 8CO2(g) + 10 H2O(g) • Shows molar and volume ratios • Questions: • How many moles of oxygen are required to produce 35 moles of water? • How many liters of butane does it take to completely react with 50 liters of oxygen?
Try It • What volume of oxygen (O2) is needed to react with solid sulfur to form 3.5 L of SO2 gas? O2(g) + S(s) SO2(g) so 3.5 L O2 yields 3.5L SO2 • What volume of oxygen is needed to completely combust 2.36 L of methane gas? CH4(g) +2O2 (g)CO2(g) + 2H2O(g) 2.36 L CH4 X 2 mol O2/ 1 mol CH4 = 4.72 L O2
Volume and Mass Problems • A balanced equation indicates both moles and volume (for gases) and can convert either to mass • Example: N2(g) + 3H2(g) 2NH3(g) If 5.00 L of nitrogen reacts completely at a constant pressure and temperature of 3.00 atm and 298 K, how many grams of ammonia are produced?
Try It • Given: NH4NO3(s) N20(g) + 2H2O(g) Calculate the mass of solid ammonium nitrate that must be used to obtain .100 L of dinitrogen oxide gas at a pressure of 3.00 atm and a temperature of 15o C. Hints: change .100 L of N20 into moles calculate moles of NH4NO3 that reacted calculate the mass of the NH4NO3
Answers • NH4NO3(s) N20(g) + 2H2O(g) PV = nRT or n = PV / RT n = 3.00 atm x .100 L / 288 K x .0821 atm.L/K.mol = .0127 mol N2O .0127 mol NH4NO3 .0127 mol NH4NO3 x 79.035 g/mol = 1.00 g NH4NO3
Try It 2. Solid potassium metal will react with Cl2 gas to form ionic potassium chloride. How many liters of Cl2 gas are needed to completely react with .204 g of potassium at STP? 2K(s) + Cl2(g) 2KCl(aq) Steps: convert grams of K into moles determine moles of Cl2 needed convert moles of Cl2 to liters
Answers 2K(s) + Cl2(g) 2KCl(s) .204 g K x 1 mol / 39.098 g = .00522 mol K .00522mol K x 1 mol Cl2 / 2 mol K = .00261mol Cl2 PV = nRT so V = nRT/P = .00261mol Cl2 x .0821atm.L/K.mol x 273 K / 1.00 atm = .0585 L or 5.85 x 10-2 L or 58.5 ml