Georgia Military CollegeCHE 105Stoichiometry Answer Key

1. Write the equation that expresses in acceptable chemical shorthand the following statement: “Iron can be made to react with molecular oxygen (O2) to give iron oxide with the formula Fe2O3” 4Fe + 3O2  2Fe2O3 2. Balance the following reactions: a. Ca(OH)2 + 2HCl CaCl2 + 2H2O b. 2AgNO3 + CaCl2  Ca(NO3)2 + 2AgCl c. 2Fe2O3 + 3C  4Fe + 3CO3 d. 2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2 e. 2C4H10 + 13O2  8CO2 + 10H2O f. Mg(OH)2 + 2HBr  MgBr2 + 2H2O g. Al2O3 + 3H2SO4  Al2(SO4)3 + 3H2O h. 2KHCO3 + H3PO4  K2HPO4 + 2H2O + 2CO2 i. C9H10O + 14O2  9CO2 + 10H2O Stoichiometry/limiting reactants 3. Chlorine is used by textile manufacturers to bleach cloth. Excess chlorine is destroyed by its reaction with sodium thiosulfate, Na2S2O3: Na2S2O3(aq) + 4Cl2(g) + 5H2O(aq)  2NaHSO4(aq) + 8HCl(aq) Compound Na2S2O3 4Cl2 5H2O 2NaHSO4 8HCl Amount, mol 1 4 5 2 8 Molar mass, g/mol .5 Mass, g 158 4x71 = 284 5x18=90 2x120=240 8x36.5=292 a.