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Stoichiometry Study Guide
1. 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 reaction.
d. mechanism involved in the reaction.
2. Fewer steps are required to solve stoichiometry problems when the reactant is
given in
a. grams and the product is sought in grams.
b. moles and the product is sought in moles.
c. grams and the product is sought in liters.
d. liters and the product is sought in number of atoms.
3. If one knows the mole ratio of a reactant and product in a chemical reaction, one
can
a. estimate the energy released in the reaction.
b. calculate the speed of the reaction.
c. calculate the mass of the product produced from a known mass of reactant.
d. decide whether the reaction is reversible.
4. In the chemical equation wA + xB → yC + zD, if one knows the mass of A and
the molar masses of A, B, C and D, one can determine
a. the mass of any of the reactants and products.
b. the mass of B only.
c. the total mass of C and D only.
d. the total mass of A and B only.
5. In the reaction 2Al2O3 → 4Al + 3O2, what is the mole ratio of aluminum to
oxygen?
a. 10:6
b. 3:4
c. 2:3
d. 4:3
6. In the reaction Ca + Cl2 → CaCl2, what is the mole ratio of chlorine to calcium
chloride?
a. 2:3
b. 2:1
c. 1:2
d. 1:1
7. A chemical reaction involving substances A and B stops when B is completely
used. B is the
a. excess reactant.
b. limiting reactant.
c. primary reactant.
d. primary product.
8. The substance not completely used up in a chemical reaction is known as the
a. limiting reactant.
b. limiting product.
c. excess reactant.
d. excess product.
9. What mass in grams of sodium hydroxide is produced if 20.0g of sodium metal
react with excess water according to the chemical equation 2Na(s) + 2H2O →
2NaOH(aq) + H2(g)?
a. 45.2g NaOH
b. 34.8g NaOH
c. 21.2g NaOH
d. 55.6g NaOH
10. What mass of 1 – chlorpropane (C3H7Cl) is produced if 400g of propane react
with excess chlorine gas according to the equation C3H8 + Cl2 → C3H7Cl + HCl?
a. 712g C3H7Cl
b. 521g C3H7Cl
c. 984g C3H7Cl
d. 317g C3H7Cl
11. How many grams of ammonium sulfate can be produced if 30.0 mol of H2SO4
react with excess NH3 according to the equation 2NH3(aq) + H2SO4(aq) →
(NH4)2SO4(aq)?
a. 5555g (NH4)2SO4
b. 1200g (NH4)2SO4
c. 3960g (NH4)2SO4
d. 7843g (NH4)2SO4
12. What is the ratio of the actual yield to the theoretical yield, multiplied by 100%?
a. Mole ratio
b. Percentage yield
c. Avogadro yield
d. Excess yield
13. What is the maximum possible amount of product obtained in a chemical
reaction?
a. Theoretical yield
b. Percentage yield
c. Mole ratio
d. Actual yield
14. For the reaction Cl2 + 2KBr → 2KCl +Br2, calculate the percentage yield if 200g
of chlorine react with excess potassium bromide to produce 410g of bromine.
a. 73.4%
b. 82.1%
c. 91.0%
d. 98.9%
15. For the reaction Mg + 2HCl → H2 + MgCl2, calculate the percentage yield of
magnesium chloride if 100g of magnesium react with excess hydrochloric acid to
yield 330g of magnesium chloride.
a. 71.8%
b. 74.3%
c. 81.6%
d. 84.2%
16. The reaction of 100g of salicylic acid with excess acetic anhydride produces 50g
of aspirin, acetylsalicylic acid, according to the equation C7H6O3 + C4H6O3 →
C3H8O4 + C2H4O2. What is the percentage yield for this reaction?
a. 38.5%
b. 64.3%
c. 81.2%
d. 12.4%
17. In the decomposition of hydrogen peroxide, the percentage yield of oxygen is
93.0%. What is the actual yield in grams of oxygen if you start with 100g of
H2O2? The reaction proceeds according to the following equation 2H2O2(l) →
2H2O(l) + O2(g).
a. 55.8g O2
b. 94.2g O2
c. 43.7g O2
d. 21.7g O2
18. Sulfur in gasoline can produce sulfuric acid, H2SO4, according to the two-step
process shown below. For each 125g of sulfur in gasoline, how many moles of
H2SO4 will be produced?
S(s) + O2(g) → SO2(g)
2SO2(g) + 2H2O(l) + O2(g) → 2H2SO4(aq)
a. 4.5mol
b. 2.1mol
c. 3.9mol
d. 1.4mol
19. How many atoms are in a sample of an element whose mass in grams is
numerically equal to the atomic mass?
a. 1
b. 6.02
c. 1 x 1023
d. 6.02 x 1023
20. What kind of substance is represented by a formula unit?
a. Ionic
b. Molecular
c. Nonmetallic
d. Radioactive
21. In what units is molar mass typically expressed?
a. Kg
b. L
c. Amu
d. g/mol
22. The sum of the percentages in the percentage composition of a substance equals
a. 100.
b. the molar mass.
c. the molar volume.
d. Avogadro’s number.
23. The simplest whole-number ratio of the atoms of the elements in a compound is
given by the
a. formula mass.
b. molar mass.
c. molecular formula.
d. empirical formula.
24. What is the empirical formula of water?
a. HO
b. H2O
c. H2O2
d. HO2
25. How many atoms of carbon are present in ethanol (C2H5OH)?
a. 2
b. 4
c. 1.20 x 1024
d. 1.81 x 1024
26. What is the total mass of carbon in 2 molecules of butane (C4H10)?
a. 48.0 g
b. 96.0 g
c. 32.0g
d. 81.0g
27. How many atoms of hydrogen are present in 4 molecules of butane (C4H10)?
a. 40
b. 80
c. 1.2 x 1025
d. 2.4 x 1025
28. Determine the percentage composition of magnesium carbonate (MgCO3).
a. 50% Mg, 25% C, 25% O
b. 28.8% Mg, 14.2% C, 56.9% O
c. 10.3% Mg, 26.6% C, 72.1% O
d. 14.7% Mg, 34.2% C, 51.1%
29. An 11.78 gram sample of an unknown compound is decomposed and analyzed.
The procedure produces 0.36 g of hydrogen, 3.73 g of phosphorus, and 7.69
grams of oxygen. Determine the percentage composition of the compound.
a. 3.0% H, 31.7% C, 65.3% O
b. 1.8% H, 34.6% C, 63.6% O
c. 5.2% H, 24.4% C, 70.4% O
d. 2.1% H, 39.3% C, 58.6% O
30. A sample of a molecular compound was analyzed and found to contain 9.09
grams of carbon, 1.52 grams of hydrogen, and 14.40 grams of fluorine. The
molar mass of the compound is 66.0g/mol, determine the molecular formula of
the compound.
a. CH2F
b. C4H8F4
c. C6H12F6
d. C2H4F2