1. Stoichiometry Review Guide

2. What is stoichiometry?

3. In stoichiometry, chemists are mainly concerned with
Multiple Choice
In stoichiometry, chemists are mainly concerned with
A. the types of bonds found in compounds.
B. mass relationships in chemical reactions.
C. energy changes occurring in chemical reactions.
D. the speed with which chemical reactions occur.

4. Name 2 ways we have used stoichiometry.

5. What do the coefficients in a chemical equation tell you?

6. Multiple Choice
Assume ideal stoichiometry in the reaction: CH4 + 2O2  CO2 + 2H2O
If you know the mass of CH4, you can calculate
A. only the mass of CO2 produced.
B. only the mass of O2 reacting.
C. only the mass of CO2 + H2O produced.
D. the mass of O2 reacting & CO2 + H2O produced.

7. Which properties must be the same on both sides of a chemical equation?

8. Which properties don’t have to be the same on both sides of a chemical equation?

9. 2C2H6 + 7O2  4H2O + 6CO2 Write 3 mole ratios

10. 2C2H6 + 7O2  4H2O + 6CO2 “For every ___ moles of oxygen and ___ moles of ethane that react, ___ moles of carbon dioxide and ___ moles of water are formed.”

11. Multiple Choice
Which mole ratio for the equation 6Li + N2  2Li3N is incorrect?
A C.
B D.
2 mol Li3N
1 mol N2
6 mol Li
2 mol N2
1 mol N2
6 mol Li
2 mol Li3N
6 mol Li
1 mol N2
6 mol Li

12. 2C2H6 + 7O2  4H2O + 6CO2 Calculate in your head how many moles of carbon dioxide are formed if you begin with 8 mols of ethane.

13. What is a limiting reactant?

14. Multiple Choice N2 + 3H2  2NH3
For the reaction below, how many moles of N2 are required to produce 18 mol NH3?
N2 + 3H2  2NH3
A C. 18
B D. 36

15. What is an excess reactant?

16. What is the Limiting Reactant. 2C2H6 + 7O2  4H2O + 6CO2 7. 49 mol 24
What is the Limiting Reactant? 2C2H6 + 7O2  4H2O + 6CO mol mol

17. Multiple Choice 2Na + Cl2  2NaCl
What mass of NaCl can be produced by the reaction of 0.75 mol Cl2?
2Na + Cl2  2NaCl
A g C. 44 g
B. 1.5 g D. 88 g

18. Why is the LR not necessarily the reactant with the least amount of moles?

19. Multiple Choice CaCO3  CaO + CO2
What mass of CO2 can be produced from 25.0 g CaCO3 given the decomposition reaction
CaCO3  CaO + CO2
A g C g
B g D g

20. How many moles of each product can be formed
How many moles of each product can be formed? 2C2H O2  4H2O + 6CO mol mol

21. Multiple Choice
If a chemical reaction involving substances A and B stops when B is completely used up, then B is referred to as the
A. excess reactant.
B. primary reactant.
C. limiting reactant.
D. primary product.

22. How many grams of water can be formed. 2C2H6 + 7O2  4H2O + 6CO2 7
How many grams of water can be formed? 2C2H6 + 7O2  4H2O + 6CO mol mol

23. Multiple Choice
If a chemist calculates the maximum amount of product that could be obtained in a chemical reaction, he or she is calculating the
A. percentage yield.
B. mole ratio.
C. theoretical yield.
D. actual yield.

24. How many moles excess reactant remain after the reaction
How many moles excess reactant remain after the reaction? 2C2H O  4H2O + 6CO mol mol

25. Short Answer
What data are necessary to calculate the percentage yield of a reaction?

26. Extended Response
A student makes a compound in the laboratory and reports an actual yield of 120%. Is this result possible? Assuming that all masses were measured correctly, give an explanation.

27. Extended Response
Benzene, C6H6, and hydrogen bromide, HBr, as shown below. When 40.0 g of benzene are reacted with 95.0 g of bromine, 65.0 g of bromobenzene is produc with bromine, Br2, to produce bromobenzene, C6H5Br
C6H6 + Br2  C6H5Br + HBr
a. Which compound is the limiting reactant? b. What is the theoretical yield of bromobenzene? c. What is the reactant in excess, and how much remains after the reaction is completed? d. What is the percentage yield?