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Chemistry 2202 Unit 1 Test 2
page 1
Chemistry 2202
Unit 1 Test 2
2005-06
Directions: This test consists of two parts. Part 1 is multiple choice and Part 2 is
constructed response. Write all responses in the spaces provided. Please
use a pen. Submit ALL pages of this test (including any pages containing
workings/outlines) to your supervising teacher upon completion.
Part 1 – Multiple Choice: Complete each item using the answer form on page 4.
(1 point per item)
1.
Which statement about the synthesis of sodium chloride is correct?
2 Na (s)
A.
B.
C.
D.
2.
+
Cl2(g)
2 NaCl (s)
Two atoms of sodium will react with two molecules of chlorine.
Two formula units of sodium produce two atoms of sodium chloride.
Two grams of sodium will react with one gram of chlorine.
Two moles of sodium produce two moles of sodium chloride.
According to the information given, what mass of chlorine is required to react?
2 Na (s)
+
Cl2 (g)
12.5 g
A.
B.
C
D.
3.
→
→
2 NaCl (s)
?
31.8 g
9.65 g
19.3 g
25.6 g
38.6 g
Most modern gas barbeques use the heat produced by the combustion of propane.
1 C3H8(g)
+
5 O2(g)
→
3 CO2(g)
+
4 H2O (g)
Which mole ratio should be used to determine the amount of carbon dioxide
produced by the combustion of 3.6 mol O2 ?
A.
B.
4.
1 mol C3H8
C.
4 mol H2O
3 mol CO2
D.
4 mol H2O
3 mol CO2
5 mol O2
5 mol O2
3 mol CO2
In the metallurgy of galena, PbS, the first step involves the roasting of the ore.
2 PbS (s)
+
3 O2(g)
→
2 PbO (s)
+
2 SO2(g)
How many moles of oxygen should be consumed if 0.500 mol PbS are roasted?
A. 0.333 mol
B. 0.500 mol
C. 0.750 mol
D. 1.50 mol
Chemistry 2202 Unit 1 Test 2
5.
Gravimetric stoichiometry refers to quantitative analysis involving which quantity?
A.
B.
C.
D.
6.
formula units
mass
molecules
volume
How many moles of sulfur should react with 75.4 g of potassium?
2 K (s)
A.
B.
C.
D.
7.
+
S (s)
+
S (s)
→
K2S (s)
27.6 g
55.1 g
110 g
221 g
What amount of ammonia, NH3, will be produced by the reaction of 0.230 mol of
hydrogen, H2, at STP?
N2(g)
A.
B.
C.
D.
+
3 H2(g)
→
2 NH3(g)
0.153 mol
3.43 mol
7.73 mol
10.3 mol
How many moles of ammonia, NH3, will be produced by the complete reaction of
16.4 L of hydrogen at STP?
N2(g)
A.
B.
C.
D.
10.
K2S (s)
What mass of potassium sulfide will be produced if 0.500 mol of sulfur reacts
completely?
A.
B.
C.
D.
9.
→
0.964 mol
1.18 mol
3.85 mol
5.73 mol
2 K (s)
8.
page 2
+
3 H2(g)
→
2 NH3(g)
0.488 mol
0.732 mol
1.10 mol
146 mol
Which term means ‘the chemical species that is completely consumed in a
chemical reaction’ ?
A.
B.
C.
D.
excess species
gravimetric species
limiting species
product species
Chemistry 2202 Unit 1 Test 2
11.
page 3
A reaction occurs between copper metal and ions of dissolved silver nitrate.
Cu (s)
2 AgNO3 (aq)
+
→
Cu(NO3 )2(aq)
+
2 Ag (s)
When the reaction is complete, the addition of sodium chloride to the reaction
vessel causes the formation of another solid, silver chloride. What species is
correctly identified?
A.
B.
C.
D.
12.
copper metal – excess species
copper nitrate – limiting species
silver chloride – limiting species
silver nitrate – excess species
A mixture of 6.00 mol of lead and 4.00 mol of sulfur is heated:
Pb (s)
+
2 S (s)
→
PbS2(s)
What is in excess?
A. 1.00 mol S
B. 2.00 mol Pb
C. 4.00 mol Pb
D. Neither Pb nor S is in excess.
13. Sally and Harry complete a laboratory activity that involves the production and
collection of a precipitate by filtration. They discover that the amount collected is
less than what was expected. They identify and list the most likely errors in the
activity. Which is a systematic error?
A.
B.
C.
D.
14.
Susan and Bart react solutions of lead(II) nitrate and potassium iodide. Their prelab
calculations indicate that 5.63 g of lead(II) iodide would be formed. After filtration
they weighed out 6.11 g of lead(II) iodide. How would you refer to the 6.11 g
mass?
A.
B.
C.
D.
15.
calculating the expected mass incorrectly
decanting too much solution into the funnel
filtering the solution before the reaction was finished
using a reactant that had been contaminated at some time.
the actual yield
the expected yield
the percent yield
the theoretical yield
Calculations indicate that 3.76 g of copper should be formed in a single
replacement reaction. The recovered mass of copper is 3.20 g. What is the
percent yield for the reaction?
A.
B.
C.
D.
14.9 %
85.1 %
100 %
118 %
Chemistry 2202 Unit 1 Test 2
page 4
Name: ______________________________________ Site: ___________________________________
Chemistry 2202 - Unit 1 Test 2
Part 1: For each item, circle the letter corresponding to your choice.
1.
A
B
C
D
6.
A
B
C
D
11.
A
B
C
D
2.
A
B
C
D
7.
A
B
C
D
12.
A
B
C
D
3.
A
B
C
D
8.
A
B
C
D
13.
A
B
C
D
4.
A
B
C
D
9.
A
B
C
D
14.
A
B
C
D
5
A
B
C
D
10. A
B
C
D
15.
A
B
C
D
Part 2: Write your responses in the spaces provided. Show all workings and be neat!
16.
Verify that the Law of Conservation of Mass is upheld in the reaction:
2 Fe (s)
+
3 Cl2(g)
2 mol × 55.85 g mol
+
3 mol × 70.90 g mol
111.70 g
+
→
(3)
2 FeCl3(s)
=
2 mol × 162.20 g mol
212.70 g
=
324.40 g
324.40 g
=
324.40 g
Law of conservation of mass is verified because mass of products equals mass of
reactants.
17.
Nitrogen gas is produced in an automobile air bag by the decomposition of sodium azide,
NaN3.
2 NaN3(s)
→
3 N2(g)
+
2 Na (s)
Calculate the volume of N2 produced at STP when 124 g NaN3 decomposes.
Convert given to moles :
nG =
m
124 g
=
= 1.9071055 mol
M 65.02 gmol
Apply Mole Ratio : nW = 1.9071055 mol NaN3 ×
3 mol N2
= 2.8606583 mol
2 mol NaN3
Calculate Wanted Amount : v = n × V = 2.8606583 mol × 22.4 L mol = 64.078745 L
The volume of nitrogen gas that should be produced is 64.1 L.
(4)
Chemistry 2202 Unit 1 Test 2
page 5
Name: ______________________________________ Site: ___________________________________
18.
Solid iron reacts in a single replacement reaction with copper(II) chloride solution.
Fe (s)
(a)
+
CuCl2(aq)
→
FeCl2(aq)
+
Cu (s)
In the laboratory, students react 4.25 g Fe with excess copper(II) chloride and collect
4.00 g of Cu product.
i)
Calculate the theoretical yield of copper.
Convert given to moles :
nG =
(3)
m
4.25 g
=
= 0.0760966 mol
M 55.85 gmol
Apply Mole Ratio : nW = 0.0760966 mol Fe ×
1 mol Cu
= 0.0760966 mol
1 mol Fe
Calculate Wanted Amount : m = n × M = 0.0760966 mol × 63.55 g mol = 4.84 g
The theoretical yield of copper metal is 4.84 g.
ii)
Calculate the percent yield.
% yield =
(1)
Actual Yield
4.00 g
× 100% =
× 100% = 82.6%
Theoretical Yield
4.84 g
The percent yield is 82.6%
(b)
Give two possible reasons why the percent yield is not 100%.
(2)
Some of the copper precipitate may have been lost during the filtration procedure.
(random). The iron that was used may not have been pure (systematic).
19.
The first step in the production of nitric acid is to react ammonia with oxygen to form
nitrogen monoxide and water vapor.
4 NH3 (g) + 5 O2(g) → 4 NO (g) + 6 H2O (g)
Identify the excess and limiting species if 0.128 mol NH3 is mixed with 1.50 mol O2. Justify
your answer.
(2)
Calculate moles of oxygen needed to react with 0.128 mol of ammonia:
5 mol O2
nW = 0.128 mol NH3 ×
= 0.160 mol
4 mol NH3
Since the required amount of oxygen is more than the amopunt available to react,
oxygen is limiting and ammonia is in excess.
The problem can also be solved by calculating moles of ammonia needed:
4 mol NH3
nW = 0.150 mol O2 ×
= 0.120 mol
5 mol O2
The amount available (0.128 mol) is greater than the amount needed (0.120), so NH3
is in excess.