Ch 9 Stoichiometry Review
Remember the two roadmaps and how to use them.
grams ↔ moles ↔ particles
grams ↔ moles ↔ moles ↔ grams
You must know how to calculate molar masses (Ch 8) and balance equations (Ch 6).
Be sure to read and review all notes (Ch 9.1, 9.2, 9.3, 9.4, 9.5) and worksheets.
Review how to use mole ratios in a stoichiometry problem (Ch 9.1,
9.2 and WS 1).
Review how to set up and solve stoichiometry problem (Ch 9.3 notes and WS 2 and WS 3). Remember, units have to cancel out in the stoichiometry math.
Identify the limiting reactant in a stoichiometry problem (Ch 9.4 notes and WS 4). Determine how many moles and grams of the excess reactant were unused.
Use the percent yield formula to solve for percent yield, actual yield, or theoretical yield (Ch 9.5 notes and WS 5).
Problems:
1. Calculate molar masses for the following compounds: (You will use two of them in problem 8.)
a.Na3PO4 b.Ca(NO3)2c. Ca3(PO4)2 d. NaNO3
2.The combustion of a sample of butane, C4H10(lighter fluid), produced 2.46 grams of water.
2 C4H10 + 13O2 8CO2 + 10H2O
a.How many moles of water formed?
b.How many moles of butane burned?
c.How many grams of butane burned?
d.How many moles of oxygen were used?
e.How many grams of oxygen were used?
f.How many molecules of water were formed?
3.Use the following balanced equation. How many grams of sodium sulfate will be produced by the complete reaction of 200.0 grams of sodium hydroxide?
2 NaOH + H2SO4 2 H2O + Na2SO4
4.a.Use the following balanced equation. Calculate the theoretical yield of iron if 165.2 grams of Fe2O3 are completely reacted
Fe2O3 + 3 H2 2 Fe + 3 H2O
b.What is the percent yield if 109.6 grams of iron are actually obtained by the chemist?
5.a.A chemist sets up a process to produce 250.0 grams of lithium sulfate. How many grams of lithium nitrate does she need to add to excess lead(IV) sulfate to produce the desired amount of product?
Pb(SO4)2 + 4 LiNO3 Pb(NO3)4 + 2 Li2SO4
excess x grams 250.0 grams
b.What was the actual yield if the chemist recovered only 73.45% of her intended target yield?
6.a.Use the following balanced equation. Identify the limiting reactant when 1.150 grams of HgO react with 12.46 grams of Cl2.
HgO + 2 Cl2 HgCl2 + Cl2O
b.How many grams of each product can be formed?
c.How many grams of the excess reactant do not react?
7.Boron trifluoride reacts with hydrogen gas to produce solid boron and hydrogen fluoride gas. In this reaction 40.0 grams of boron trifluoride are reacted with 5.00 grams of hydrogen gas.
a.Write the balanced equation.
b.Identify the limiting reactant.
c.Calculate the mass of boron produced (theoretical yield).
d.If the percent yield of boron is 72.6%, what was the actual yield of boron?
8.Examine the unbalanced reaction below:
Na3PO4(aq) + Ca(NO3)2(aq) Ca3(PO4)2(s) + NaNO3(aq)
a.If 30.00 grams of calcium nitrate are reacted with excess sodium phosphate, what is the theoretical yield of calcium phosphate?
b.If 15.45 grams of calcium phosphate are recovered, calculate the percent yield.
9.A chemist combines 50.00 grams of solid magnesium with excess aqueous silver(I) nitrate. Silver precipitates out and magnesium nitrate remains dissolved. The chemist recovers 92.35% of the possible silver produced.
a.Write the balanced equation for the reaction.
b.What is the actual yield of silver for this reaction? (Hint: what do you have to calculate first?)
10.The percent yield for a particular chemical reaction is 86.3%. If the actual yield is 15.34 grams what was the theoretical yield for the product?