Department of Chemistry, University of Bahrain, Chemy 102, 2

Department of Chemistry, University of Bahrain, Chemy 102,
2nd Sem_12-13_Laboratory Exam, Time: 75 min
Name __________________________________ ID _______________ Sec ____
Given: specific heat of water = 4.18 J/g·°C.
+
pH = – log [H ]
R = 8.314 J K– 1 mol –1
__________________________________________________________________
Q1
[3 marks]
The following plot is for the reaction of 30.0 mL of 0.750 M CuSO4 (aq) with
excess zinc powder (zinc was added at t = 3 min).
What is ΔH per mole of CuSO4 ?
80
Temperature / oC
70
60
50
40
30
20
10
0
5
10
15
Time / min
1
20
25
30
Q2
[4 marks]
The pH profile for the titration of a weak acid (HB) with NaOH is shown in the
figure below.
14
13
12
28 30
35
40
45
50
11
26
10
9
25
pH
8
7
6
5
10
5
4
3
20 22
15
24
0
2
1
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54
Volume of NaOH / mL
a) What is the pH at the equivalence point?
b) What is the value of K a for the weak acid?
c) Using the table below, determine which one indicator is most suitable to be
used to locate the equivalence point in this titration.
Color
Indicator
in acid
in base
pH range
thymol blue
bromophenol blue
methyl orange
methyl red
chlorophenol blue
bromothymol blue
cresol red
phenolphthalein
red
yellow
orange
red
yellow
yellow
yellow
colorless
yellow
bluish purple
yellow
yellow
red
blue
red
reddish pink
1.2−2.8
3.0−4.6
3.1−4.4
4.2−6.3
4.8−6.4
6.0−7.6
7.2−8.8
8.3−10.0
2
Q3
[2 marks]
(a) Which of the following ions will undergo hydrolysis reaction?
[circle the correct answers]
Ni2 , PO43 – , I
+
–
, ClO3– , K , Mg 2
b) Write a hydrolysis reaction for NH 4
Q4
+
+
+
[2 marks]
Is the solution at the end point of H2SO3−NaOH titration acidic, basic, or neutral?
Explain using net ionic chemical equations.
Q5
(4 marks)
Potassium permanganate reacts with oxalate ions in acidic solution as follows:
5C2O42– (aq) + 2MnO4– (aq) + 16H+ (aq) → 10CO2 (g) + 8H2O (l) + 2Mn2+ (aq)
A 0.120-g sample containing oxalate is titrated against 0.0200 M KMnO4 solution.
It was found that 19.5 mL of KMnO4 were needed to react with all the oxalate.
What is the percentage of oxalate in the sample?
3
Q6
(4 marks)
ln k
-7
-8
-9
-10
-11
-12
-13
-14
-15
-16
1/T(K)
4
0.0039
0.0038
0.0037
0.0036
0.0035
0.0034
0.0033
0.0032
0.0031
0.0030
Use the plot below to calculate the activation energy for the reaction of acetone
with iodine.
Q7
(5 marks)
Consider the following model where structures imply geometry and where lone
pairs are not shown.
A
B
E
D
C
F
i)
The molecular geometry of B is
ii)
The molecular geometry of C is
iii)
The molecular geometry of E is
iv)
The molecular geometry of F is
v)
The bond angel(s) in D is/ are
vi)
The bond angel(s) in G is/ are
vii)
The number of lone pair(s) in A is/are
viii)
The number of lone pair(s) in F is/are
ix)
The polar structures are
5
G