CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2012/13
Module Title:
Engineering Chemistry
Module Code:
CHEM6001
School:
School of Building & Civil
Programme Title:
Bachelor of Engineering (Honours) in Structural Engineering
Programme Code:
CSTRU_8_Y4
External Examiner(s):
Internal Examiner(s):
Dr. Roger P West, Mr. Jack O Leary
Mr. Ian O Sullivan
Instructions:
Answer all Questions.
Students may use course notes and “Mathematical
Formula & Tables”
Duration:
2 hours
Sitting:
Autumn 2013
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have
received the correct examination.
If in doubt please contact an Invigilator.
Section A
1. When the pH of a solution changes from 6 to 3, the solutions acidity changes by
what order of magnitude? Given that pH = -log[H+]
(2 Marks)
2. Use LeChâtelier's Principle to predict the shift that occurs when the fluorine
concentration is decreased for the following system at equilibrium. Assume all
other factors remain constant.
2B(s) + 3F2(g)↔ 2BF3(g) + 45kJ
(3 Marks)
3. A reaction has an equilibrium constant K equal to 1.0 × 10 -5 at a certain
temperature. What can be said about the ‘position’ of equilibrium?
(2 Marks)
4. For the given reaction, we start with 5.50 moles of aluminum and 10.0 moles of
chlorine. How many moles of chlorine will be left over at the end of the
reaction?
2Al(s) + 3Cl2(l)  2AlCl3(s)
(5 Marks)
5. Determine as accurately as you can the mass (g) of one atom of
28
14
Si given that
1 amu = 1.6606 x 10-24 g. Knowing the mass of one atom subsequently determine
the mass of one mole of
28
14
Si .
(5 marks)
6. A nerd in a lab has carried out an experiment to determine the atomic mass of
silicon (Si), which he thinks consists of three naturally occurring isotopes in the
following abundances
Isotope abundance (%)
28
14
Si
92.23
29
14
Si
4.68
30
14
Si
3.09
Assuming in this case that the mass of a proton and a neutron are both equal to
1 amu and that the mass of an electron is negligible, determine the molecular
mass of Si. Compare this value to the mass presented in the periodic table.
(5 marks)
7. How many atoms are there in 35 g of gold (Au)?
(5 marks)
8. A beaker contains 35 g of H2O. How many moles of H2O are there in the beaker?
How many Hydrogen (H) atoms are there in this sample?
(5 marks)
9. What are the electron configurations of Ni, Mg, P and Cl. Explain the ‘order of
orbital filling’ What do these configurations tell us about how these elements are
likely to react?
(6 Marks)
10. Plot a graph of the first ionization energy (kJ/mole) of the first 20 elements Vs
Atomic Number and comment on any trends observed.
(8 Marks)
11. Show with the aid of a ‘planetary diagram’ how an ion of sodium is formed?
(4 marks)
Section B
Q12
a. For the equation given, how many grams of hydrogen are needed to react with
70.0 g of nitrogen?
1. N2(g) + 3H2(g)  2NH3 (g) + 92 kJ
b. If 10.0 g of calcium hydroxide were reacted with 30.0 mL of 6.00 M HCl,
according to the equation given, how much water is formed?
1. Ca(OH)2(s) + 2HCl(aq)  CaCl2(aq) + 2H2O(l)
c. A chemist reacts 50.0 grams of aluminum metal with 150.0 grams of chlorine gas
according to the un-balanced chemical equation below. She recovers 175.0
grams of aluminum chloride product. What is her percent yield?
1. Al + Cl2  AlCl3
(25 Marks)
Q13
You are attempting to determine the percentage of water in crystalline copper
sulphate in the laboratory and you have taken the following measurement in the
laboratory
Mass of crystalline copper sulphate
2g
Mass of anhydrous copper sulphate
1.33 g
a. Calculate the molecular mass of Crystalline Copper Sulphate (CuSO4.5H2O) with
the aid of the following table
b. Calculate the molecular mass of anhydrous Crystalline Copper Sulphate.
c. Determine the percentage of CuSO4 in CuSO4.5H2O
d. Determine the percentage H2O present in CuSO4.5H2O
e. Show how the percentage H2O present in CuSO4.5H2O is experimentally
determined.
f. Why was it necessary to have a completely clean crucible at the beginning of the
experiment?
g. Why was it necessary to ensure that no CuSO4 is lost from the crucible due to
spluttering?
h. Why was it necessary to repeatedly heat, cool and weigh the crucible? What is
the function of the desiccator?
i.
What is the % error in your experimental data?
j.
Suggest a reason for why there were inaccuracies in your calculations?
(25 Marks)