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TIER 6 Combine the knowledge of gases and solutions to perform stoichiometric calculations

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Gas Stoichiometry Sample Problem Propane, C 3 H 8, is a gas that is sometimes used as a fuel for cooking and heating. The complete combustion of propane occurs according to the following balanced equation. C 3 H 8 (g) + 5O 2 (g) → 3CO 2 (g) + 4H 2 O(g) (a) What will be the volume, in liters, of oxygen required for the complete combustion of L of propane? (b) What will be the volume of carbon dioxide produced in the reaction? Assume that all volume measurements are made at the same temperature and pressure.

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Sample Problem Solution Given: balanced chemical equation; V of propane = L Unknown: V of O 2 Solution: Because all volumes are to be compared at the same conditions, volume ratios can be used like mole ratios. Gas Stoichiometry: VOLUME TO VOLUME.350L C 3 H 8 X 3L CO 2 = 1.05 L CO2 1 L C 3 H 8

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Gas Stoichiometry:VOLUME TO MASS Sample Problem Calcium carbonate, CaCO3, also know as limestone, can be heated to produce calcium oxide (lime) and industrial chemical with a wide variety of uses. CaCO3 (s) CaO (s) + CO2(g) How many grams of calcium carbonate must be decomposed to produce 5.00L of carbon dioxide gas at STP?

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Sample Problem Solution Given: - Balanced chemical equation; CaCO3 (s) CaO (s) + CO2(g) -V of carbon dioxide= 5.00 L -STP conditions Unknown: g of CaCO 3 At STP 1 mole of gas occupies 22.4 L 5.00L x 1 mole CO 2 =.223 moles CO L.223 moles CO 2 x 1 mole CaCO3 =.223 moles CaCO 3 1mole CO 2

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PROBLEM: How many liters of H2 gas at STP can be produced by the reaction of 4.6 g Na and excess water according to the following equation? 2Na(s) + 2 H 2 O(l) H 2 (g) + 2 NaOH (aq)

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Sample Problem: MASS TO VOLUME Tungsten is produced by the reaction of tungsten oxide with hydrogen. WO 3 (s) + 3H 2 (g) W(s) + 3 H 2 O(l) How many liter of hydrogen gas at 35oC and.980 atm are needed to react completely with 875 g of tungsten oxide?

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Sample Problem Solution Given: balanced chemical equation WO 3 (s) + 3H 2 (g) W(s) + 3 H 2 O(l) -P is.980 atm -T is 35 o C -mass of WO 3 Unknown: V of hydrogen gas 875 g WO 3 x 3 mol H 2 = 11.3 mole H g WO 3 V = nRT = (11.3 mol)(.0821) (308K) = 292L H 2 P.980

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PROBLEM: How many liters of gaseous carbon monoxide at 27oC ad.247 atm can be produced from the burning of 65.5g of carbon according to the following equation? 2C(s) + O 2 (g) 2CO(g)

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SOLUTION STOICHIOMETRY

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SAMPLE PROBLEM: In a recent lab, a 2M hydrochloric acid was reacted with 2.00 g of Magnesium. Mg(s) + 2HCl MgCl 2 (ag) + H 2 (g) (a)How many cm 3 of hydrochloric acid would be needed to react all the magnesium with out any acid excess. (b) How many dm 3 of hydrogen gas could be produced at STP

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SAMPLE PROBLEM SOLUTION GIVEN: Balanced equation: Mg(s) + 2HCl MgCl 2 (ag) + H 2 (g) -mass of Mg =2.00g -Molarity of HCl = 2mol dm -3 -STP conditions UNKNOWN: (a) V of HCl solution (b) V of H 2 gas (a)2.00g Mg x 1mole Mg x 2 mole HCl x 1 dm 3 HCl =.08 dm 3 = 80 cm g Mg 1 mole Mg 2 mol HCl (b)2.00g Mg x 1 mole Mg x 1 mole H 2 x 22.4 dm 3 = 1.84 dm g Mg 1 mole Mg 1mole

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PROBLEM: In a recent lab, a 3M nitric acid was reacted with 3.50 g of zinc. Zn(s) + 2HNO 3 Zn(NO 3 ) 2 (ag) + H 2 (g) (a)How many cm 3 of nitric acid would be needed to react all the zinc with out any acid excess. (b) How many dm 3 of hydrogen gas could be produced at STP

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