Name: ________________________
Fall 2004
INSTRUCTIONS:
1)
2)
3)
4)
5)
6)
1.
Student Number: _____________________
Chemistry 2100 In-Class Test 2 (B)
___/ 30 marks
WHITE TEST
Please read over the test carefully before beginning.
Write your first and last name on every page of the test.
Marks will be deducted for improper use of significant figures.
If your work is not legible, it will be given a mark of zero.
Show your work for all calculations. Answers without supporting
calculations will not be given full credit.
You have 30 minutes to complete this test.
Assign oxidation states to each element, and identify which atom(s) are oxidized and
which are reduced.
[3 marks]
0
+4 -2
+1 -2
+2
-2 +1
+2
-2 +1
Cd + NiO2 + 2 H2O → Cd(OH)2 + Ni(OH)2
oxidized: ______Cd__________
2.
reduced: _______Ni
(of NiO2)___________
Lithium metal reacts with molecular nitrogen to give lithium nitride. Write the balanced
chemical equation for this reaction. Assign oxidation states to each element, and identify
which atom(s) are oxidized and which are reduced.
[4 marks]
0
0
+1
-3
6 Li + N2 → 2 Li3N
oxidized: ____Li__________
3.
(of N2)___________
Balance the following reaction equations:
(a)
2 P +
(b)
C7H8O2 +
(c)
2 SO2
(d)
reduced: __________N
+
5 I2
→ 2 PI
8 O2
→ 7 CO
O2
Na2SiO3 + 8 HCl
[4 marks]
5
→
2
+ 4 H2O
2 SO3
→ H SiCl
2
6
+
2 NaCl + 3 H2O
Name: ________________________
4.
Student Number: _____________________
Before the year 1997, Canadian pennies were made of pure copper. If a penny made
before 1997 contains 2.67 x 1022 atoms of copper, what is its mass?
[2 marks]
mass = 2.67 × 1022 atoms ×
1 mol
× 63.546 g
23
6.02 × 10 atoms
1 mol
mass = 2.82 g
***3 significant figures***
5.
The reaction equation for the combustion of diesel (C16H34) is shown below:
2 C16H34 + 49 O2
226.448 g/mol
(a)
32 CO2 + 34 H2O
44.009 g/mol
If 120 g of diesel is combusted with excess oxygen, what is the theoretical yield of CO2
(in grams)?
[3 marks]
mass CO2 = 120 g C16H34 × 1 mol C16H34 × 32 mol CO2 × 44.009 g CO2
226.448 g C16H34 2 mol C16H34
1 mol CO2
mass CO2 = 373 g CO2
***3 significant figures***
(b)
If 110.25 g of CO2 is actually produced, what is the % yield of the reaction?
[1 mark]
percent yield =
actual yield
× 100%
theoretical yield
= 110.25 g CO2 × 100%
373 g CO2
percent yield = 29.6%
***3 significant figures (since 3 were carried down from question 4a)***
Name: ________________________
6.
Student Number: _____________________
Circle and identify the functional group(s) in each of the following molecules. Do not
identify the alkane groups.
[4 marks]
e.g.
O
H
Be careful of spelling. Mistakes often turn
H
one word into another.
C
H
C
O
H
C
H
H
ester
haloalkane
(a)
(b)
O
H
H
N
C
H
CH3CH2C
CCH3
H
C
C
H
(c)
Cl
H
alkyne
H
OH
amide
alcohol
7.
For the following pairs of molecules, indicate whether they are constitutional isomers,
identical compounds or neither.
[4 marks]
isomers, identical or
neither?
identical
and
O
O
and
CH3CH2CH2CNH2
isomers
CH3CCH2CH2NH2
CH3
and
CH3CH2CHCHCH2NH2
CH3CH2CH2CH2CH2CH2NH2
neither
CH3
H H
H
H
C
H
C
H
O
C
H
H
H
C
H
H
and
H
O
C
H
H
H H
H
C
C
C
H H
H
isomers
Name: ________________________
8.
Student Number: _____________________
For the following hypothetical endothermic reaction, draw an arrow (→ or ←) to indicate
the direction in which each change will push the equilibrium.
[1 mark]
heat
+
A + B
C
(a)
addition of heat:____________________
(b)
addition of C:______________________
9.
Write the balanced chemical equation for the reaction described by the following
equilibrium constant expression.
[2 marks]
Keq =
O2 +
10.
4 HBr
[Br2]2[H2O]2
[O2] [HBr]4
2 Br2
+ 2 H 2O
If you needed to choose a polar solvent to use for thin layer chromatography (TLC),
which would be a better choice, chloroform (CHCl3) or carbon tetrachloride? [2 marks]
chloroform
(The dipoles in CCl4 all cancel out; the dipoles in CHCl3 do not. Therefore, of the
two molecules, only CHCl3 has a net dipole and only CHCl3 is a polar molecule.)