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## UNIT 2: REVIEW

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**UNIT 2: REVIEW**TIER 6 Combine the knowledge of gases and solutions to perform stoichiometric calculations**Gas Stoichiometry**• Sample Problem • Propane, C3H8, 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. • C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) • (a) What will be the volume, in liters, of oxygen required for the complete combustion of 0.350 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.**Gas Stoichiometry: VOLUME TO VOLUME**• Sample Problem Solution • Given:balanced chemical equation; V of propane = 0.350 L • Unknown:V of O2 • Solution:Because all volumes are to be compared at the same conditions, volume ratios can be used like mole ratios. .350L C3H8 X 3L CO2= 1.05 L CO2 1 L C3H8**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?**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 CaCO3 At STP 1 mole of gas occupies 22.4 L 5.00L x 1 mole CO2 = .223 moles CO2 22.4 L .223 moles CO2 x 1 mole CaCO3 =.223 moles CaCO3 1mole CO2**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 H2O(l) H2(g) + 2 NaOH (aq)**Sample Problem: MASS TO VOLUME**Tungsten is produced by the reaction of tungsten oxide with hydrogen. WO3 (s) + 3H2 (g) W(s) + 3 H2O(l) How many liter of hydrogen gas at 35oC and .980 atm are needed to react completely with 875 g of tungsten oxide?**Sample Problem Solution**Sample Problem Solution Given: balanced chemical equation WO3(s) + 3H2 (g) W(s) + 3 H2O(l) -P is .980 atm -T is 35oC -mass of WO3 Unknown: V of hydrogen gas 875 g WO3 x 3 mol H2= 11.3 mole H2 231.84 g WO3 V = nRT= (11.3 mol)(.0821) (308K) = 292L H2 P .980**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) + O2(g) 2CO(g)**SAMPLE PROBLEM:**In a recent lab, a 2M hydrochloric acid was reacted with 2.00 g of Magnesium. Mg(s) + 2HCl MgCl2 (ag) + H2 (g) (a)How many cm3 of hydrochloric acid would be needed to react all the magnesium with out any acid excess. (b) How many dm3 of hydrogen gas could be produced at STP**SAMPLE PROBLEM SOLUTION**GIVEN: Balanced equation: Mg(s) + 2HCl MgCl2 (ag) + H2 (g) -mass of Mg =2.00g -Molarity of HCl = 2mol dm-3 -STP conditions UNKNOWN: (a) V of HCl solution (b) V of H2 gas 2.00g Mg x 1mole Mg x 2 mole HCl x 1 dm3HCl = .08 dm3 = 80 cm3 24.31g Mg 1 mole Mg 2 mol HCl 2.00g Mg x 1 mole Mg x 1 mole H2x 22.4 dm3= 1.84 dm3 24.31 g Mg 1 mole Mg 1mole**PROBLEM: In a recent lab, a 3M nitric acid was reacted**with 3.50 g of zinc. Zn(s) + 2HNO3 Zn(NO3 )2(ag) + H2 (g) (a)How many cm3 of nitric acid would be needed to react all the zinc with out any acid excess. (b) How many dm3 of hydrogen gas could be produced at STP