Name_______________________
Stoichiometry Practice Test
Gallium consists of two isotopes of masses 68.95 amu and 70.95 amu with abundances of 60.16% and
39.84%, respectively. What is the average atomic mass of gallium?
a)
b)
c)
d)
e)
69.95
70.15
71.95
69.75
69.55
ANS: d)
How many moles of hydrogen sulfide are contained in a 35.0-g sample of this gas?
a) 2.16 mol
b) 1.03 mol
c) 7.43 mol
d) 1.06 mol
e) 1.058 mol
ANS: b)
Balanced chemical equations imply which of the following?
a)
b)
c)
d)
e)
ANS:
Numbers of molecules are conserved in chemical change.
Numbers of atoms are conserved in chemical change.
Volume is conserved in chemical change.
a and b
b and c
b)
Iron is biologically important in the transport of oxygen by red blood cells from the lungs to the various
13 red
organs of the body. In the blood of an adult human, there are approximately 2.60
blood cells with a total of 2.90 g of iron. On the average, how many iron atoms are present in each
red blood cell? (molar mass (Fe) = 55.85 g)
a) 8.33 x 10–10
b) 1.20 x 109
c) 3.12 x 1022
d) 2.60 x 1013
e) 5.19 x 10–2
ANS: b)
For which compound does 0.256 mole weigh 12.8 g?
a)
b)
c)
d)
e)
C2H4O
CO2
CH3Cl
C2H6
Something that is not here
ANS: c)
Roundup, an herbicide manufactured by Monsanto, has the formula C3H8NO5P. How many moles of
molecules are there in a 500.-g sample of Roundup?
a)
b)
c)
d)
e)
0.338
1.75
2.96
84.5
none of these
ANS: c)
A given sample of xenon fluoride contains molecules of a single type XeFn, where n is some whole
20 molecules of XeF weigh 0.311 g, calculate n.
number. Given that 9.03
n
a) 1
b) 2
c) 4
d) 2007
e) 2008
ANS: c)
How many oxygen atoms are there in 1.55 ng of Ca3(PO4)2?
a) 3.01 x1012
b) 1.20 x1013
c) 3.01 x1018
d) 1.21 x1016
e) 2.41 x1013
ANS: e)
Suppose the reaction is carried out starting with 103 g of Ca3(PO4)2 and 75.0 g of H2SO4. Which
substance is the limiting reactant?
a) Ca3(PO4)2
b) H2SO4
c) CaSO4
d) H3PO4
e) none of these
ANS: b)
In balancing an equation, we change the __________ to make the number of atoms on each side of the equation
balance.
a)
b)
c)
d)
e)
ANS:
formulas of compounds in the reactants
coefficients of compounds
formulas of compounds in the products
subscripts of compounds
none of these
b)
What is the coefficient for water when the following equation is balanced?
As(OH)3(s) + H2SO4(aq)  As2(SO4)3(aq) + H2O(1)
a)
b)
c)
d)
e)
ANS:
1
2
4
6
12
d)
One molecule of a compound weighs 2.03  10–22 g. Its molar mass is:
a)
b)
c)
d)
e)
ANS:
48.0 g/mol
92.1 g/mol
114 g/mol
122 g/mol
none of these
d)
The limiting reactant in a reaction
a)
b)
c)
d)
e)
ANS:
has the lowest coefficient in a balanced equation.
is the reactant for which you have the fewest number of moles.
has the lowest ratio of moles available/coefficient in the balanced equation.
has the lowest ratio of coefficient in the balanced equation/moles available.
none of these
c)
Given the equation 3A + B  C + D, you react 2 moles of A with 1 mole of B. Which of the following is true?
a)
b)
c)
d)
e)
ANS:
A is the limiting reactant because of its higher molar mass.
A is the limiting reactant because you need 3 moles of A and have 2.
B is the limiting reactant because you have fewer moles of B than A.
B is the limiting reactant because 3 A molecules react with 1 B molecule.
Neither reactant is limiting.
b)
Which of the following compounds has the same percent composition by mass as styrene, C8H8?
a)
b)
c)
d)
e)
ANS:
acetylene, C2H2
benzene, C6H6
cyclobutadiene, C4H4
-ethyl naphthalene, C12H12
all of these
e)
Ammonium carbonate contains what percent nitrogen by mass?
a)
b)
c)
d)
e)
ANS:
14.6%
17.9%
29.2%
34.8%
none of these
c)
Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula?
a)
b)
c)
d)
e)
ANS:
C3H5O2
C3H3O4
C2HO3
C2H5O4
C3HO3
a)
What is the coefficient for oxygen when the following equation is balanced?
NH3(g) + O2(g)  NO2(g) + H2O(g)
a)
b)
c)
d)
e)
ANS:
3
6
7
12
14
c)
What is the subscript of aluminum in the formula of aluminum phosphate?
a)
b)
c)
d)
e)
ANS:
1
2
3
4
0
a)
Give the empirical formula for the following compounds:
a)
______________
b)
______________
c)
______________
d)
______________
ANS: a) CH b) CH2 c) CH2O d) C3H5O
Answer the following questions to proper sig figs. Please CIRCLE your answer and provide a balanced
equation when necessary. Thank you!
1. How many liters of nitrogen gas are needed to react with 44.8 liters of hydrogen gas to produce
ammonia gas? Balanced equation:
2. If two balloons are each filled with equal volumes (7.5 L), one with nitrogen gas other with
hydrogen gas. Which reactant is limiting and how much (g) ammonia gas will be produced?
3. 10.0 grams of calcium carbonate was produced when carbon dioxide was added to 5.00 M lime
water (calcium hydroxide in solution). What volume of carbon dioxide at STP was needed?
Balanced equation:
4. When 11.2 liters of hydrogen gas is made by adding zinc to sulfuric acid, what mass of zinc is
needed? Balanced equation:
5. How many grams of carbonic acid is produced when 55 liters of carbon dioxide is pressed into 12.1
moles of water? (Hint: determine limiting reagent first)
magnesium hydroxide + ammonium sulfate
magnesium sulfate + water + ammonia
6. How much (g) magnesium hydroxide do you need to use in the above reaction to produce 500 liters
of ammonia? Balanced equation:
7. How much (g) strontium bromide is needed to add to chlorine gas to produce 5.23 liters of liquid
bromine? (Bromine = 3.119 g/cm3) Balanced equation:
8. If 32.7 grams of zinc combines with 38.0 mL of hydrochloric acid to produce ZnCl2 and hydrogen
gas.(HCl: d=1.19 g/mL). Balanced equation:
Determine the limiting reagent:
How many grams of ZnCl2 are produced?
If the actual yield was 121. 2 grams, then what is the percent yield of zinc chloride?