Return to Principles of Chemistry Homepage


Solving stoichiometry problems should not be a puzzle!

1. Phosphorous, P4, burns in oxygen to form diphosphorous pentaoxide.

a. Write and balance a chemical equation representing this chemical reaction.
b. How many moles of diphosphorous pentaoxide are formed by the combustion of 3.25 moles of P4?
6.5 moles of diphosphorous pentaoxide
c. When the product is added to water it forms phosphoric acid. How many moles of water are consumed if 2.33 moles of P2O5 are consumed?
6.99 moles of water

2. Calculate the number of grams of LiOH formed when 2.55 moles of Li3N react with water?
____ Li3N + ____ H2O
____ LiOH + ____ NH3
183 grams of lithium hydroxide

3. What mass, grams, of calcium carbonate is required to produce 1.57 moles of carbon dioxide?
     ____ CaO + ____ CO2
157 grams of calcium carbonate

4. How many grams of carbon dioxide are formed when 5.53 grams of ethyl alcohol, C2H5OH, are produced from glucose, C6H12O6, according to the equation below.
_____ C6H12O6 ___ C2H5OH + ____ CO2
5.3 grams of carbon dioxide

5. How many grams of magnesium metal are required to react with 35 grams of nitrogen gas to produce magnesium nitride?
90 grams of magnesium nitride

5. How many grams of magnesium metal are required to react with 35 grams of nitrogen gas to produce magnesium nitride?
90 grams of magnesium nitride

6. For the reaction shown below, 1.26 grams of methane, CH4, were formed, how many grams of aluminum carbide was consumed?

_____ Al4C3 + ____ HCl _____ CH4 + ____ AlCl3
3.8 grams of aluminum carbide

7. In the above problem how many liters of methane would be produced if 4.5 grams of aluminum carbide reacts with an excess of HCl? The density of methane is 0.554 grams per Liter.
2.7 liters of methane

8. Aluminum reacts with hydrochloric acid to produce aluminum chloride and hydrogen gas.. How many liters of hydrogen gas could be produced from a bar of aluminum that is 15 cubic inches. The density of hydrogen is 0.0899 grams per liter and the density of the aluminum is 2.702 grams per cc.
820 liters of hydrogen gas

 9. Four moles of aluminum carbide and six moles of HCl are mixed in a reaction vessel and the reaction in problem 6 is carried out. How many moles of methane are produced?
1.5 moles of methane

10. For the reaction given below, 7.54 moles of sodium hydroxide are mixed with 4.8 moles of H2S. How many moles of sodium sulfide are formed?
____ NaOH + _____ H2S
____ Na2S + ____ H2O
3.77 moles of sodium sulfide

11. What mass of lead(II) bromide are formed when a solution containing 2.45 grams of potassium bromide are mixed with a solution containing 5.86 grams of lead(II) nitrate?
____ KBr + ____ Pb(NO3)2
____ PbBr2 + ___ KNO3

3.85 grams of lead(II) bromide

12. How many grams of carbon dioxide would be formed from the combustion of 20 grams of propane and 75 grams of oxygen.

___ C3H8(g) + ____ O2(g) ____ CO2(g) + ___ H2O(g)
59.4 grams of carbon dioxide

13. Determine the percent yield for the following reaction, if a student uses 5 moles of Cl2(g) and obtains 1.9 moles of C6H4Cl2 crystals.
____ C6H6(l) + ___ Cl2(g)
___ C6H4Cl2(g) + ____ HCl(g)

14. If the following process produces a yield of 89% sulfur dioxide by mass, how many moles of sulfur dioxide are obtained upon heating 84 grams of zinc bisulfite?
__ Zn(HSO3)2(s)
___ ZnO(s) + __ SO2(g)+ ___ H2O(g)
0.66 moles of sulfur dioxide realized

15. 11.98 grams of potassium phosphate are needed for use in an experiment using souble phosphates. How many grams of H3PO4 will be needed to react with an excess of potassium hydroxide in order to obtain 11.98 grams of K3PO4? Assume one obtains 78% yield of K3PO4 .

7.01 grams of phosphoric acid

16. Aspirin, C9H8O4, is produced by Dow Chemical Corporation from C7H6O3 and C4H6O3. What quantity of pure C7H6O3 would be needed to manufacture 1500 ton of aspirin? The yield for their process is 91%.
___ C7H6O3 + __ C4H6O3
___ C9H8O4 + __ HC2H3O2
2.5 x 106 pounds of C7H6O3

17. Determine the percent yield for the reaction of calcium hydroxide with nitric acid , if a mixture of 98 grams of HNO3 and 119 grams of Ca(OH)2, yielded 105 grams of calcium nitrate.

18. The following reaction is used in an industrial process for making sodium sulfate.
____ NaCl + ____ H2SO4
_____Na2SO4 + ___ HCl
The process uses salt cake (88% pure sodium chloride). The process produces an industrial grade sodium sulfate that is 96% Na2SO4 . How many ton of the industrial grade sodium sulfate will be produced from 2.75 ton of salt cake.
3.06 ton of industrial grade sodium sulfate

19. How many moles of potassium chlorate would be required to supply the proper amount of oxygen gas needed to burn 2.45 moles of methane, CH4 ?

2 KClO3 2 KCl + 3 O2(g)

CH4 + 2 O2(g) CO2(g) + 2 H2O

3.27 moles of potassium chlorate

20. The preparation of HOCN is given below, How many grams of isocyanic acid, HOCN, can be prepared from 12.5 grams of KCN. Assume 100% yields for both reactions.

CuCl2 + 4 KCN K2[Cu(CN)2] + C2N2 + 2 KCl
C2N2 + H2O

2.07 grams of isocyanic acid

21.. In the reactions given above in problem 20, what mass of KCN would be required to obtain 2.07 grams of HOCN? You have been informed that the first reaction actually occurs with 85% yield and the second with only 69% yield.
21.3 grams of KCN