Practice Problems - Stoichiometry

Practice Problems - Stoichiometry 1. Problem: Determine the mass of 6.00 atoms of Americium (found in smoke detectors) 2. Empirical & Molecular Formula Problems: a) Determine the molecular formula for Freon C318: Freon C318 has a molecular mass of 200.00 g/mol and a % composition of 24.02% C by mass and remainder is F b) Determine the molecular formula for the following compound that has a molecular mass of 238.80 g/mole and a % composition of 43.64% P by mass and the reminder is O. c) Determine the molecular formula for ethanol given the following information: 5.00 grams of ethanol is burned in excess oxygen to yield 9.55 grams of carbon dioxide and 5.87 grams of water. The molecular mass of ethanol is 46.0 grams. Ethanol’s molecular formula is composed of C, H and O atoms only. 3. Problems: Balance the following reactions ___NO + ___O2 → ___NO2 ___H2O2 → ___H2O + ___O2 ___S + ___O2 → ___SO3 ___NH3 + ___Cl2 → ___NH4Cl + ___NCl3 ___ C2H5OH + ___O2 → ___H2O + ___CO2 ___C6H12O6 + ___ O2 → ___H2O +___ CO2 ___SbCl3 + ___H2O →___SbOCl +___ HCl ___ Mg(ClO)2 + ___ AlPO4 → ___ Mg3(PO4)2 + ___ Al(ClO)3 ___Fe + ___S → ___Fe2S3 ___ZnS + ___O2 → ___ZnO + ___SO2 ___N2O4 + ___N2H4 → ___H2O + ___N2 ___C8H18 + ___O2 → ___H2O + ___CO2 ___CH4 + ___Cl2 → ___HCl + ___CHCl3 4. Stoichiometry Problems a) The chief component of glass is silicon dioxide. To dissolve silicon dioxide, hydrofluoric acid is used, and the following products are made, solid silicon tetrafluoride and water vapor. Determine how many grams of silicon tetrafluoride would be produced if 63.4 grams of hydrofluoric acid reacted with excess silicon dioxide? Determine the actual grams of HF produced a 75% yield was observed SiO2 (s) + HF (g) → SiF4 (s) + H2O (g) b) 18.10 grams of ammonia gas was reacted with 90. 40 grams of solid cupric oxide to produce nitrogen gas + copper metal + water vapor. Determine the % yield of this reaction if 8.90 grams of nitrogen gas was produced. Determine the amount in grams of excess reagent from this reaction. c) When solid iron (III) oxide reacts with heated carbon monoxide, iron metal and carbon dioxide is produced. Determine the actual mass of iron metal produced, in grams, given that the theoretical yield for the iron metal was determined to be 0.600 moles of iron metal and the % yield of the overall reaction was 85.1% d) Cisplatin is an antitumor drug. Given the following information, determine the % yield when 35.50 grams of cisplatin is produced. 65.50 g K2PtCl4 + 5.10 g NH3 (g) -------- > K+ (aq) + Pt(NH3)2Cl2 (s) e) A 0.900-gram sample of magnesium metal is placed in a flask containing 0.250 grams of nitrogen gas. The flask is heated, and 0.785 grams of magnesium nitride is produced. The chemical equation for this reaction is given below: Magnesium metal + nitrogen gas → magnesium nitride(g) i. ii. iii. Write a balanced chemical equation for this reaction, using chemical formulas. Calculate the percent yield for this chemical reaction. Determine in micrograms which reactant, if any was in excess? f) The thermite reaction was once used by the railroads to weld rails. The thermite reaction is: iron (III) oxide (s) + aluminum (s) + heat → aluminum oxide (s) + iron (l) i. ii. iii. Using chemical formulas, balance the above redox reaction. Determine the mass of liquid iron produced when 25.0 grams of aluminum metal and 85.0 grams of iron (III) oxide solid are mixed and heated together. Determine the percent yield of the reaction if 45.8 grams of liquid iron is produced.