Basic Stoichiometry Post Lab Homework Exercises Answers

Basic Stoichiometry Post Lab Homework Exercises Answers Basic Stoichiometry PostLab Homework Exercises Answers This document provides answers and explanations for a set of basic stoichiometry postlab homework exercises The exercises cover fundamental concepts in stoichiometry including mole conversions masstomass calculations limiting reactants and percent yield Exercise 1 Mole Conversions Question 11 How many moles of sodium chloride NaCl are present in 250 grams of NaCl Answer 1 Find the molar mass of NaCl Na sodium 2299 gmol Cl chlorine 3545 gmol Molar mass of NaCl 2299 gmol 3545 gmol 5844 gmol 2 Use the molar mass as a conversion factor 250 g NaCl 1 mol NaCl 5844 g NaCl 0428 mol NaCl Question 12 Calculate the mass in grams of 0750 moles of potassium hydroxide KOH Answer 1 Find the molar mass of KOH K potassium 3910 gmol O oxygen 1600 gmol H hydrogen 101 gmol Molar mass of KOH 3910 gmol 1600 gmol 101 gmol 5611 gmol 2 Use the molar mass as a conversion factor 0750 mol KOH 5611 g KOH 1 mol KOH 421 g KOH Exercise 2 MasstoMass Calculations Question 21 What mass of magnesium oxide MgO is produced when 500 grams of magnesium Mg reacts completely with excess oxygen O2 2 Balanced Chemical Equation 2 Mg O2 2 MgO Answer 1 Convert grams of Mg to moles of Mg 500 g Mg 1 mol Mg 2431 g Mg 0206 mol Mg 2 Use the mole ratio from the balanced equation to find moles of MgO 0206 mol Mg 2 mol MgO 2 mol Mg 0206 mol MgO 3 Convert moles of MgO to grams of MgO 0206 mol MgO 4030 g MgO 1 mol MgO 829 g MgO Question 22 How many grams of calcium carbonate CaCO3 are needed to produce 100 grams of carbon dioxide CO2 in the following reaction Balanced Chemical Equation CaCO3 CaO CO2 Answer 1 Convert grams of CO2 to moles of CO2 100 g CO2 1 mol CO2 4401 g CO2 0227 mol CO2 2 Use the mole ratio from the balanced equation to find moles of CaCO3 0227 mol CO2 1 mol CaCO3 1 mol CO2 0227 mol CaCO3 3 Convert moles of CaCO3 to grams of CaCO3 0227 mol CaCO3 10009 g CaCO3 1 mol CaCO3 227 g CaCO3 Exercise 3 Limiting Reactants Question 31 200 g of sodium Na reacts with 150 g of chlorine gas Cl2 to produce sodium chloride NaCl What is the limiting reactant and how many grams of NaCl are produced Balanced Chemical Equation 2 Na Cl2 2 NaCl Answer 1 Convert grams of Na and Cl2 to moles 200 g Na 1 mol Na 2299 g Na 0870 mol Na 150 g Cl2 1 mol Cl2 7090 g Cl2 0212 mol Cl2 2 Determine the limiting reactant Using the mole ratio from the balanced equation calculate the moles of NaCl produced by each reactant 3 Na 0870 mol Na 2 mol NaCl 2 mol Na 0870 mol NaCl Cl2 0212 mol Cl2 2 mol NaCl 1 mol Cl2 0424 mol NaCl Cl2 produces fewer moles of NaCl so it is the limiting reactant 3 Calculate the grams of NaCl produced using the moles of the limiting reactant 0424 mol NaCl 5844 g NaCl 1 mol NaCl 248 g NaCl Exercise 4 Percent Yield Question 41 A chemist reacts 100 g of zinc Zn with excess hydrochloric acid HCl to produce 155 g of zinc chloride ZnCl2 Calculate the theoretical yield and percent yield for this reaction Balanced Chemical Equation Zn 2 HCl ZnCl2 H2 Answer 1 Calculate the theoretical yield Convert grams of Zn to moles of Zn 100 g Zn 1 mol Zn 6538 g Zn 0153 mol Zn Use the mole ratio from the balanced equation to find moles of ZnCl2 0153 mol Zn 1 mol ZnCl2 1 mol Zn 0153 mol ZnCl2 Convert moles of ZnCl2 to grams of ZnCl2 0153 mol ZnCl2 13628 g ZnCl2 1 mol ZnCl2 209 g ZnCl2 theoretical yield 2 Calculate the percent yield Percent Yield Actual Yield Theoretical Yield 100 Percent Yield 155 g ZnCl2 209 g ZnCl2 100 742 Conclusion These exercises demonstrate basic stoichiometric calculations which are essential for understanding chemical reactions and predicting the amount of product formed Mastering these concepts will provide a strong foundation for more advanced chemistry topics