Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

Stoichiometry Problems Set #3

Stoichiometry Exercises #3


Stoichiometry  Simple

1. Lead(II) sulfide, PbS, reacts with oxygen gas to produce lead(II) oxide and sulfur dioxide. If 0.500 moles of O2 were consumed using this chemical reaction, how many grams of lead(II) oxide would be produced? (Ar: O=16; Pb=207; S=32) Ans: 74.3  

2 PbS + 3 O2  2 PbO + 2 SO2

2. Potassium chlorate, KClO3, decomposes when heated to produce potassium chloride and oxygen gas. If 2.50 grams of KClO3 were heated in a test tube, how many grams of oxygen gas should be given off? (Ar: O=16; Cl=35.5; K=39) Ans: 0.980 g

2 KClO 2 KCl + 3 O2

Percent Yield


3. The reaction between 15.8 g of NH3 and excess oxygen gas produces 21.8 g of NO gas and some water.  Determine the percent yield. (Ar: O=16; N=14; H=1) Ans: 78.19

4 NH+ 5 O24 NO + 6 H2O

4. For the balanced equation shown below, if the reaction of 77.0 grams of CaCN2 produces 27.1 grams of NH3, what is the percent yield? (Ar: O=16; N=14; H=1; Ca=40; C=12) Ans: 82.8

CaCN+ 3 H2 CaCO+ 2 NH3

5. For the balanced equation shown below, if the reaction of 91.3 grams of C3H6 produces at 81.3% yield, how many grams of CO2 would be produced? (Ar: O=16; H=1; C=12) Ans: 233

2 C3H+ 9 O6 CO+ 6 H2O

6.  For the balanced equation shown below, if the reaction of 20.7 grams of CaCO3 produces 6.81 grams of CaO, what is the percent yield?(Ar: O=16; Ca=40; C=12) Ans: 58.75

 CaCOCaO + CO2

7. Given the following equation and  you start with 389.4 g of Al2(SO3)3 and you isolate 212.4 g of Na2SO3, what is your percent yield for this reaction?
(Ar: O=16; Al=27; Na=23; S=32; H=1) Ans: 42.42%

Al2(SO3)3    +  6 NaOH    3Na2SO3    +   2 Al(OH)3

Limiting Reactant


8.       When copper (II) chloride reacts with sodium nitrate, copper (II) nitrate and sodium chloride are formed. If 15 grams of copper (II) chloride react with 20 grams of sodium nitrate, how much sodium chloride can be formed?

CuCl2     +      NaNO3    Cu(NO3)2    +      NaCl




Aluminum reacts with oxygen gas to produce aluminum oxide.

4 Al + 3 O2  2 Al2O3

Sketch 2 containers representing beakers, one on the left and another on the right of an arrow. Draw 10 atoms of aluminum and 6 molecules of oxygen gas in the container on the left. In the right container, sketch the contents after the reaction is complete.(Ar: Al=27; O=16)

  1. What is the limiting reactant? 
  2.  How many atoms or molecules of the excess reactant remain?
10. If 21.4 g of aluminum is reacted with 91.3 g of iron(III) oxide, the products will be aluminum oxide and iron metal.(Ar: Al=27; O=16; Fe=56)

Fe2O3  + 2 Al  Al2O3 + 2 Fe

  1. What mass of iron will be produced?
  2. How much NON LIMITING REACTANT is left?
11. If 15 grams of copper react with 20 g of silver nitrate. How much silver can be formed? (be careful. You need to calculate the limiting reactant to be able to answer the question) (Ar: Cu=64; O=16; Fe=56)

 Cu + 2 AgNO3  Cu(NO3)2 + 2 Ag

 12.  If a reaction vessel contains 0.15 mol K2O2 and 0.10 mol H2O, what is the limiting reactant? (Ar: K=39; O=16; H=1)

 2 K2O2 + 2 H2O   4 KOH + O2