CHM 1020 Path 4 Chapter 9 Study Pack Part III

Chapter 9 Part III: Chemical Equations & Stoichiometry (Chapter 9)

F. Mole-Mole Problems Answers

F1.Mass-Mass Stoichiometric Problems- Answers

F2.Excess/Limiting Reagent Problems- Answers

F3.Per Cent Yield Problems/Impure Reagents-Answers

Chapter 9 Part F Chapter 9



Part F Mole-Mole Stoichiometry




Homework #1: Tungsten occurs in the important mineral sheelite (Calcium tungstate), which is converted to tungstic acid. Tungsten is then extracted from tungstic acid by the following (unbalanced) reaction:

H2 + H2WO4 W + H2O

How moles of hydrogen is needed to prepare 6 moles of elemental tungsten?





Homework #2: Phosphoric acid can be made by the following (unbalanced) reacti

H2O + P4O10 H3PO4

How many moles of Phosphoric acid can be prepared from the combination of 5 moles of Tetraphosphorus decoxide with excess water?








Part F2 Mass-Mass Stoichiometry

Use this concept map for Part F2 Mass-Mass Problems:











The Solution to: __?____gHg = 1.25g 1.25 gHgO









Homework #3: Toluene and nitric acid are used in the production of trinitrotoluene (TNT), an explosive:

C7H8 + HNO3 C7H5N3O6 + H2O (Unbalanced)

Calculate the mass of TNT that can be made from 192 g of C7H8 (toluene).







Homework #4: What mass of carbon dioxide is produced from the combustion of 176 grams of propane gas , C3H8 , in excess oxygen gas, O2. Water is the only other product.










Part F3 Excess-Limiting Reagent Problem



Sample Limiting Reagent Problem





Some books teach you to determine which reagent is the limit first, then do the standard gram-gram problem. The following is an example of this method.


Either works, but I prefer the method above.


Homework #5: How many grams of Calcium phosphate can be made according to the reaction (unbalanced):

CaCl2 + K3PO4 ----> Ca3(PO4)2 + KCl


by mixing a solution of 5.00 grams of CaCl2 with another containing 8.00 grams of Potassium phosphate?










Part F3 Impure Reagents/Percent Yield Problem


Homework #6: A laboratory manual calls for 13.0 grams of butanol reactant in excess sodium bromide and sulfuric acid as reactants in this reaction:

C4H9OH + NaBr + H2SO4 ------> C4H9Br + NaHSO4 + H2O


A student following these directions obtains 16.8 grams of butyl bromide (C4H9Br). What is the theoretical yield and the percent yield of this reaction?