Name: __________________________
Unit 8 Honors Chemistry Test: Stoichiometry
Choose the best answer for the following statements:
1.
Stoichiometry is the study of
a. the qualitative relationships that exist in chemical reactions.
b. the quantitative relationships that exist in chemical reactions.
c. energy changes in chemical reactions.
d. the balance of nature in chemistry.
2.
Which of the following would be investigated in stoichiometry?
a. The masses of hydrogen and oxygen in water
b. The amount of energy released in chemical reactions
c. The mass of potassium required to produce a known mass of potassium chloride
d. The types of bonds that break and form when acids react with metals
3.
A balanced chemical equation allows one to determine the
a. Mole ratio of any two substances in the reaction
b. Energy released in the reaction
c. Electron configuration of all elements in the reation
d. Mechanism involved in the reaction
4.
Identify the reactants in the following chemical equation:
Zn + CuSO4  ZnSO4 + Cu
a. zinc and copper
b. zinc and copper(II) sulfate
c. zinc sulfate and copper
d. only zinc
5.
What happens to the bonds between atoms in a substance that undergoes a chemical
reaction?
a. All single covalent bonds become double covalent bonds.
b. Some existing bonds will weaken while others will strengthen.
c. Existing bonds are broken and atoms are rearranged with the formation of new
bonds.
d. Bonds between atoms are unaffected during a chemical reaction.
6.
The total number of atoms represented by the formula (NH4)2Cr2O7 is
a. 11
b. 14
c. 16
d. 19
1
7.
A balanced equation verifies the Law of Conservation of Mass because
a. the mass of the reactants equals the mass of the products.
b. the molar masses of all substances are the same.
c. the coefficients on both sides of the equation are the same.
d. the mass of the products always equals 100 grams.
8.
After writing the chemical formulas of the reactants and products, what value should be
checked for accuracy immediately before balancing the equation?
a. coefficients
b. charges
c. subscripts
d. moles
9.
The limiting reactant in a chemical reaction
a. will have some amount unchanged, or leftover, after the reaction.
b. is completely used up in the reaction.
c. cannot be calculated without performing the reaction.
d. has no effect on the amount of product formed.
10. The ratio of the actual amount of product to the amount of product in a calculated
chemical reaction is called the
a. true yield
b. expected yield
c. actual yield
d. percent yield
11. The calculated amount of product that should be produced in a chemical reaction is
called the
a. true yield
b. theoretical yield
c. actual yield
d. percent yield
12. If the percent yield is equal to 100%, then
a. The actual yield is greater than the theoretical yield
b. The actual yield is equal to the theoretical yield
c. The actual yield is less than the theoretical yield
d. There was no limiting reactant
2
13. In the reaction, CH4(g) + 2O2(g)  CO2(g) + 2H2O(g), a mass of 25 g CO2 is produced
by reacting methane (CH4) with excess oxygen. The following expression calculates
the
a. mass of water produced.
b. minimum mass of oxygen needed.
c. moles of carbon dioxide produced.
d. moles of methane consumed.
14. To determine the limiting reactant in a chemical reaction, one must know the
a. available amount of one of the reactants.
b. amount of product formed.
c. available amount of each reactant.
d. speed of the reaction.
Refer to the following chemical equation to answer questions 15-18 on your bubble
sheet.
3 H2 (g) + N2 (g)  2 NH3 (g)
15. The molar ratio of H2 to N2 is 3:2.
a. true
b. false
16. The mass of NH3 formed when 30.0 g of H2 reacts with excess nitrogen is 120 grams.
a. true
b. false
17. If the actual yield of the above reaction is 140 g, the percent yield of NH3 is 82 percent.
a. true
b. false
18. The limiting reactant when 10.0 g of H2 reacts with 5.0 g of N2 is the nitrogen.
a. true
b. false
3
Written Test:
Review your answers for questions 15-18. If the answer was false, correct the
statement on this section of the exam. If the answer was true, you may leave it blank.
15)_______________________________________________________________________
16) _______________________________________________________________________
17) _______________________________________________________________________
18) _______________________________________________________________________
19) Explain why the conversion factor
3𝑔 𝑀𝑔(𝑂𝐻)2
6𝑔 𝐻2𝑂
cannot be used for the reaction
Mg3N2(s) + 6H2O(l) 3Mg(OH)2(aq) + 2NH3(g)
__________________________________________________________________________
____________________________________________________________________________
20) Justify why a chemical equation must be balanced to solve stoichiometry problems.
______________________________________________________________________________________________
______________________________________________________________________________________________
21)
afjC (O2 )
afjC CH4
(methane gas)
Why would the Bunsen burner flame go out if the gas valves were tightened too much?
Justify in terms of limiting/excess reactants.
__________________________________________________________________________
__________________________________________________________________________
4
22) How many grams of ammonium sulfate ((NH4)2SO4) can be produced if 30.0 mol of
H2SO4 react with excess NH3 according to the following equation:
2NH3(aq) + H2SO4(aq)  (NH4)2SO4(aq)?
23) 300.0 grams of AgNO3 and 300.0 grams of Na3PO4 are reacted according to the following
equation.
3AgNO3 + Na3PO4  Ag3 PO4 + 3 NaNO3
a. How many grams of Ag3 PO4 are produced?
b. Which substance is the limiting reactant? ____________________________
c. What is the calculated theoretical yield ? _____________________________
d. Calculate the percent yield if 130.8 grams of Ag3PO4 are actually produced. ___________
5