MODULE 2
14
WORKSHEET
WORKSHEET
CALCULATING REACTING
QUANTITIES
Syllabus reference 8.3.4
For multiple-choice questions 1–5 circle the letter corresponding to the most correct answer.
1
The balanced equation for the burning of butanol (C4H9OH) is given below:
C4H9OH(l)  6O2(g) → 4CO2(g)  5H2O(l)
The amount of oxygen needed to burn 2 mole of butanol is:
a
b
c
d
2
2 moles
4 moles
6 moles
12 moles
For the following reaction:
PbSO4(s)  H → Pb2  HSO4
Which of the following is NOT true?
a
b
c
d
3
One mole of lead sulfate produces one mole of lead ions.
The reaction takes place in water.
Both products precipitate out of solution.
The equation is balanced.
A student has two identical flasks. One flask is filled with 1 mole of carbon dioxide (CO2) at a
temperature of 25ºC and the other flask is filled with 2 moles of hydrogen (H2) at a temperature of
0ºC.
The ratio of number of molecules of CO2 to the number of molecules of H2 is:
a
b
c
d
4
4:1
2:1
1:1
1:2
The law of combining volumes was proposed by:
a
b
c
d
Dalton
Gay-Lussac
Avogardo
Newton
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5
A compound of mass 2.41 g is obtained when 1.77 g cobalt is reacted completely with oxygen. The
empirical formula of the compound is:
a
b
c
d
6
CoO
Co2O3
Co3O2
Co3O4
Large crystals of white anhydrous copper(II) nitrate are heated strongly and a particular type of
reaction occurs. The equation for the reaction is:
2Cu(NO3)2(s) → 2CuO(s)  4NO2(g)  O2(g)
5.0 moles of copper(II) nitrate are placed in a crucible and heated. The change in the amount of
substance remaining as it is heated over a period of time is shown below.
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5
4
3
2
1
0
a
0
2
4
6
8
10
��������������
12
14
How would the mass of copper(II) oxide at the end of the reaction compare with the mass of
copper(II) nitrate at the beginning of the reaction?
Mass of copper(II) oxide will be less than the mass of copper(II) nitrate.
b
How many moles of copper(II) nitrate have decomposed after six minutes?
Approximately 4 moles.
c
Calculate the total number of moles of oxygen gas formed by the time the reaction is completed.
From the balanced equation, 2 moles Cu(NO3)2 produce 1 mole O2, so 5 moles Cu(NO3)2 will produce
2.5 moles O2.
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MODULE 2 WS 14
7
The equation for the combustion of butane is:
2C4H10(g)  13O2(g) → 8CO2(g)  10H2O(l)
Calculate the number of moles of:
a
CO2 produced in the combustion of 1 mole of C4H10
4 mol
b
H2O produced in the combustion of 3 moles of C4H10
15 mol
c
O2 consumed in the combustion of 0.6 moles of C4H10
3.9 mol
8
How many moles of oxygen gas would be obtained if:
a
0.80 moles of potassium chlorate (KClO3) is decomposed by heating into potassium chloride
and oxygen?
2KClO3 → 2KCl  3O2
1.2 mol
b
0.24 moles of mercury(II) oxide is decomposed by heating into mercury and oxygen gas?
2HgO → 2Hg  O2
0.12 mol
9
0.30 moles of magnesium oxide is completely dissolved in nitric acid (HNO3) to form a solution of
magnesium nitrate. Calculate the number of moles and masses of:
a
b
nitric acid required
magnesium nitrate formed
MgO  2HNO3 → Mg(NO3)2  H2
a
n(HNO3)  0.60 mol
m (HNO3)  0.60  (1  14  3  16)  38 g
b
n(Mg(NO3)2)  0.30 mol
m (Mg(NO3)2)  0.30  (24.3  2  (14  3  16))  44 g
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10 Excess dilute sulfuric acid was added to 3.00 g of calcium carbonate (CaCO3) to form calcium
sulfate, carbon dioxide and water. Calculate the masses of:
a
sulfuric acid consumed
2.94 g
b
carbon dioxide produced
1.32 g
c
calcium sulfate formed
4.08 g
11 Dilute hydrochloric acid was added to zinc until no further reaction occurred.
a
Write a balanced equation for the reaction.
Zn(s)  2HCl(aq) → ZnCl2(aq)  H2(g)
b
If 0.012 mole of zinc chloride was formed what mass of zinc reacted?
n(ZnCl2)  0.012 mol
n(Zn)  0.012 mol
m(Zn)  0.012  65.4  0.78 g
c
What mass of zinc chloride would be produced if 0.040 mole of hydrochloric acid reacted with
excess zinc?
n(HCl)  0.040 mol
n(ZnCl2)  0.020 mol
m(ZnCl2)  0.020  (65.4  2  35.5)  2.7 g
12 What volume of oxygen is required for the complete combustion of 125 mL of butene gas (C4H8)
and what volume of carbon dioxide is formed? (All volumes are measured at the same temperature
and pressure.)
C4H8(g)  6O2(g) → 4CO2(g)  4H2O(l)
V(O2)  6  125  750 mL
V(CO2)  4  125  500 mL
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13 Nickel reacts with carbon monoxide to form gaseous nickel carbonyl. When excess nickel was
reacted with 500 mL CO, 125 mL nickel carbonyl was formed at the same temperature and
pressure. Assuming all the CO reacted, what is the formula of nickel carbonyl? Explain how you
deduced this.
Ni(CO)4
500 mL CO produced 125 mL nickel carbonyl; this means that 4 mol CO produced 1 mol
nickel carbonyl so 1 mol nickel carbonyl must contain 4 mol CO hence Ni(CO)4.
14 Propane is used as a fuel in camping stoves. The equation for the complete combustion of propane is:
C3H8(g)  502(g) → 3CO2(g)  4H2O(l)
100 mL of propane is burnt in an excess of oxygen. Calculate:
a the volume of oxygen consumed
V(O2)  100  5  500 mL
b
the volume of carbon dioxide produced
V(CO2)  100  3  300 mL
(All volumes measured at the same temperature and pressure.)
15 A silver coin was analysed and found to contain only silver and copper. 1.580 g of this coin was
dissolved in concentrated nitric acid and the resultant solution diluted. Reaction of the solution
with excess hydrochloric acid yielded 1.050 g of silver chloride. Calculate the percentage of silver
in the sample.
m(AgCl)  1.050 g
n(AgCl)  1.050 / (107.9  35.5)  7.322  103 mol
n(Ag)  7.322  103 mol
m(Ag)  7.322  103  107.9  0.79 g
%Ag  0.79 / 1.580  50.0%
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16 A sample of iron wire reacts with oxygen to form iron(III) oxide. If 3.58 g of the wire yields
5.00 g of the iron(III) oxide, calculate the percentage purity of the iron.
97.7%
17 The smelting process of chalcopyrite, CuFeS2, is represented by the following equation:
2CuFeS2(s)  5O2(g) → 2Cu(s)  2FeO(s)  4SO2(g)
If 22.0 kg of the chalcopyrite reacts and the percentage yield for this process is 95%, calculate the
mass of copper formed.
m(CuFeS2)  22 kg  2.2  104 g
n(CuFeS2)  2.2  104 / (63.5  55.8  2  32.1)  119.9 mol
n(Cu)  119.9  0.95 (95% yield)  113.9 mol
m(Cu)  113.9  63.5  7232 g  7.2 kg
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CONQUERINGCHEMISTRY PRELIM
MODULE 2 WS 14