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School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 2
QUESTION 1
1.1
(MULTIPLE CHOICE)
50 MARKS
Perform the following mathematical operation expressing your answer to
the correct number of significant figures:
(4.5 x 103 – 1.53 x 103) ÷ 34.5
(a)
0.86
(b)
86
(c)
8.6
(d)
8.60 x 10-2
(1)
1.2
Which one of the following can be classified as a homogeneous mixture?
(a)
A concrete block
(b)
A mixture of water and oil
(c)
Paint
(d)
A corroding pipe
(1)
1.3
Which one of the following properties can be classified as an extensive property?
(a)
Density of ammonia.
(b)
Ferric oxide is reddish brown in colour.
(c)
The specific heat capacity of Aluminium is 0.900 J/g oC.
(d)
The heat capacity of 60.0 g of water is 251 J/oC
(1)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 3
1.4
Identify which of the following statements are processes as a result of
chemical changes?
(a)
Sublimation of a solid at room temperature.
(b)
Insoluble in water and has a high density.
(c)
Forms a white oxide with air and its oxide is neutralized by an acid.
(d)
A substance that boils at -196 oC.
(1)
1.5
Which one of the following symbols provides more information on the
subatomic particles of the oxygen atom:
(a)
17
(b)
8O
(c)
O2-
(d)
O22-
O
(1)
1.6
The atomic number, mass number and symbol for the tin isotope with 69
neutrons is:
(a)
69
50𝑆𝑛
(b)
119
69𝑆𝑛
(c)
119
50𝑆𝑛
(d)
50
19𝑆𝑛
(1)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 4
1.7
The isotopes
35
Cl (nuclidic mass 34.9889 u) and
37
Cl (nuclidic mass 36.9659
u) are the only naturally occurring isotopes of chlorine.
The percent
distribution of the isotopes for the average atomic weight of 35.453 u is
(a)
35
Cl = 74.76 %
37
Cl=25.24 %
(b)
35
Cl = 76.52 %
37
Cl=23.48 %
(c)
35
Cl = 76.76 %
37
Cl=23.24 %
(d)
35
Cl = 77.76 %
37
Cl=23.24 %
(2)
1.8
1.9
The compounds (i) H2O2, (ii) K2O, are classified as:
(a)
(i) molecular
(ii) molecular
(b)
(i) ionic
(ii) ionic
(c)
(i) molecular
(ii) ionic
(d)
(i) ionic
(ii) molecular
(2)
What is the empirical formula for the compound formed by combination of
mercury(I) and chromate?
(a)
HgCrO4
(b)
Hg2CrO4
(c)
Hg(CrO4)2
(d)
Hg4(CrO4)
(1)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 5
1.10 Which is the correct chemical formula for chlorous acid?
(a)
HOCl3(aq)
(b)
HOCl2(aq)
(c)
HClO2(aq)
(d)
HClO(aq)
(1)
1.11 Which is the correct name for NaBrO3 according to IUPAC rules?
(a)
Sodium perbromate
(b)
Sodium bromite
(c)
Sodium bromate
(d)
Sodium hypobromite
(1)
1.12 The decomposition reaction of which compound upon heating will not produce
oxygen gas (O2(g)) as one of its products:
(a)
MgO
(b)
KClO3
(c)
CaCO3
(d)
KNO3
(2)
1.13 Which of the following compound below is an amphoteric hydroxide?
(a)
KOH
(b)
Ba(OH)2
(c)
Zn(OH)2
(d)
Ca(OH)2
(1)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 6
1.14 Which reagent below will not form a precipitate with Pb2+(aq)?
(a)
KBr(aq)
(b)
K2CrO4(aq)
(c)
NaI(aq)
(d)
HNO3(aq)
(1)
1.15 What is the mass in grams of 1 molecule of O2?
(a)
1.88 x 10-22 g
(b)
6.02 x 10
(c)
5.31 x 10-23 g
(d)
2.65 x 10-23 g
-23
g
(2)
1.16 What mass of water is formed during the combustion of 510 g of CH 3OH
with oxygen according to the following reaction?
2CH3OH(ℓ) + 3O2(g)  2CO2 + 4H2O(ℓ)
(a)
573.5 g
(b)
1154 g
(c)
649.4 g
(d)
2309 g
(2)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 7
1.17 How many grams of oxygen are needed to react with 0.300 mol S to form
SO3?
(a)
160 g
(b)
4.8 g
(c)
6.4 g
(d)
14.4 g
(2)
1.18 The elements A and Z combine to produce two different compounds A2Z3 and
AZ2. If 0.15 mole of A2Z3 has a mass of 15.9 g and 0.15 mole of AZ2 has a
mass of 9.3 g, what are the atomic masses of A and Z?
(a)
A is 39 u and Z is 36 u
(b)
A is 26 u and Z is 18 u
(c)
A is 24 u and Z is 16 u
(d)
A is 14 u and Z is 32 u
(2)
1.19 Consider the following reaction that takes place in solution
CaCl2(aq) + 2AgNO3(aq)  Ca(NO3)2(aq) + 2AgCl(s)
Suppose that we began with 200 mL of a 0.200 M solution of CaCl2
What volume of 0.500 M AgNO3 (in mL) would be needed to completely
precipitate the product?
(a)
80 mL
(b)
160 mL
(c)
400 mL
(d)
800 mL
(2)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 8
1.20 What is the final concentration of a solution when 500 mL of 1.5 M HCl is
mixed with 0.100 L of 1.00 M NaOH and diluted to 2.0 L?
(a)
0.245 M
(b)
0.325 M
(c)
1.083 M
(d)
0.600 M
(2)
1.21 What mass of H2SO4 solution (in grams) is required to completely neutralize
0.500 L of a 15 % (m/m) NaOH solution?
Assume density of NaOH at 25oC = 1.175 g mL-1.
Reaction: H2SO4(aq) + 2 NaOH(aq)  Na2SO4(aq) + 2 H2O(ℓ)
(a)
115 g
(b)
108 g
(c)
294 g
(d)
216 g
(2)
1.22 What is the reason for the increase in boiling points of the following elements?
Ne<Ar<Kr<Xe
(a)
Increase in size and decrease in dipole moment.
(b)
Increase in dipole moments and small electron clouds which are
easy to polarise.
(c)
Increase in molecular weight and large electron clouds which are easy
to polarise.
(d)
Increase in molecular weight and large nuclear charge which increases
the dispersion forces.
(2)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 9
1.23 From the following data, the order from most polar to least polar for the
following compounds are:
Compound
Boiling point
(a)
C, B, A, D
(b)
D, C, A, B
(c)
D, A, B, C
(d)
A, D, C, B
A
294
B
249
C
231
D
355
(2)
1.24 Which statement relates to intermolecular forces?
(a)
These forces are electrostatic interactions between oppositely charges
ions.
(b)
These forces are strong forces that stabilize individual molecules.
(c)
These forces are strong enough to control the bulk properties of
individual molecules.
(d)
These forces arise from the sharing of electrons between two atoms.
(1)
1.25 What is the volume (in mL) occupied by 2.12 moles of nitrogen monoxide
(NO) at 9940.8 mm Hg and 80oC ?
(a)
1064 mL
(b)
476.0 mL
(c)
4697 mL
(d)
470.0 mL
(2)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 10
1.26 The temperature of 2.5 L of a gas initially at STP is raised to 250oC at constant
volume. What is the final pressure of the gas (in atm)?
(a)
0.52 atm
(b)
1.00 atm
(c)
0.95 atm
(d)
1.90 atm
(2)
1.27
What is the standard enthalpy of formation (in kJ per mole) for the heat of
combustion of acetylene according to the following reaction?
2C2H2(g) + 5O2(g)  4CO2(g) + 2H2O(ℓ)
(a)
- 2629
(b)
-2599
(c)
-1692
(d)
-2027
(2)
1.28 The solubility of CO2 in water at 25oC and 1.0 atm is 0.034 mol/L. What is its
solubility under atmospheric conditions given the partial pressure of CO2 in air
is 0.00030 atm? Assume CO2 obeys Henry’s Law.
(a)
0.034 M
(b)
1.3 x 10-3 M
(c)
0.030 M
(d)
1.0 x 10-5 M
(2)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 11
1.29 A 44.0 g of unknown metal at 99oC was placed in a constant-pressure
calorimeter of negligible heat capacity containing 80.0 g of water (specific
heat 4.184 J/g oC) at 24.0oC. The final temperature of the system was
found to be 28.4oC.
How much of heat (q) (in Joules) is gained by the water?
(a)
2282.8
(b)
12997
(c)
1472.8
(d)
810
(2)
1.30 What is the specific heat (J/g oC ) of the unknown metal referred to in
question 1.29 above?
(a)
0.064
(b)
0.474
(c)
0.035
(d)
0.261
(2)
1.31 Soluble silicates must not be used in the presence of hard water due to its
reaction with:
-
(a) OH in hard water to form insoluble hydroxides.
(b) Mg2+ in hard water to form insoluble magnesium silicates.
(c) Ca2+ in hard water to form insoluble calcium silicates.
(d) H3O+ in hard water to form insoluble hydrates.
(2)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 12
QUESTION 2
2.1
25 MARKS
Lysine an essential amino acid in the human body contains C, H, O and N. In
one experiment the complete combustion of 2.175 g of lysine gave 3.94 g CO2
and 1.89 g of H2O. In a separate experiment, 1.873 g of lysine gave
0.436 g NH3.
Calculate the empirical formula of lysine.
(7)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 13
2.2
Consider the reaction:
MnO2 + 4HCl  MnCl2 + Cl2 + 2H2O
A mixture of 61.0 g of MnO2 and 48.2 g of HCl react:
Which reagent will be used up first? (Show relevant calculations).
(3)
2.3
Chemical analysis of a gaseous compound showed that it contained 33.0 % Si
and 67.0 % F by mass. At 35 oC, 0.210 L of the compound exerted a pressure
of 1.70 atm. If the mass of 0.210 L of the compound was 2.38 g, calculate the
molecular formula of the compound.
(5)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 14
2.4
The pressure of CO2 inside the cabin of a submarine having a volume of
2.4 x 105 L is 7.9 x 10-3 atm at 312 K. A solution of LiOH of negligible volume
is introduced into the cabin. Eventually the pressure of CO2 falls to 1.2 x 10-4
atm. How many grams of Li2CO3 forms according to the reaction:
2LiOH(aq) + CO2(g)  Li2CO3(ℓ)
(6)
School of Chemistry and Physics, UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE,
MAY/JUNE 2014 EXAMINATION
CHEM 181: CHEMISTRY FOR ENGINEERS 1A
Page 15
2.5
Calculate the standard enthalpy of formation of methanol (CH3OH) from its
elements:
C(graphite) + 2H2(g) + ½ O2(g)  CH3OH(ℓ)
Given the following heats of combustion:
CH3OH(ℓ) +
3
2
O2(g)  CO2(g) + 2H2O(ℓ)
Horxn = -726.4 kJ/mol
C(graphite) + O2(g)  CO2(g)
Horxn = -393.5 kJ/mol
H2(g) + ½ O2(g)  H2O(ℓ)
Horxn = -285.8 kJ/mol
(4)