Chemistry 100 Summer Session
Date : August 13, 1998 G. Marangoni
This Final Exam is a three-hour exam.
Read over the entire exam before beginning. Do those questions that you find easiest in the
beginning. Proceed through the exam from the easier questions to the harder ones.
Ration your time according to the value of each question.
There should be 22 different questions, the VSEPR Tables, and a periodic table for your
calculations. If this exam does not contain 22 questions, notify the instructor immediately. Part I
of the exam contains short answer questions. Part II contains long answer questions.
ANSWER ALL QUESTIONS ON THE EXAM PAPER PROVIDED. All necessary
information may be found on a page at the end of the exam. Please use only the back of the test
for rough work and calculations.
READ ALL QUESTIONS CAREFULLY
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 2
Part I - Answer these questions in the space provided. Show all your work in arriving
at the final answer. Marks are indicated in [ ].
1. Will a solution of sodium acetate and hydrochloric acid work as an acid-base buffer?
Explain briefly. [4 marks]
2. Calculate the enthalpy change for the following reaction given that the fH = -110.5
kJ/mole. [4 marks]
2 C (s) + O2 (g) 2 CO (g)
3. Which of the following molecules or ions will not obey the filled valence shell rule?
Explain. [4 marks]
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 3
4. For the dissolution of certain liquid in water [4 marks]
A (l) A (aq)
the solution process release energy (solH is negative). What can we say about the magnitude
of the solute-solvent interactions?
5. What do we mean by the electronegativity of an atom? How is the electronegativity
difference used to determine the bond polarity? [4 marks]
6. Calculate the osmotic pressure of a 1.00 M NaCl solution at 298 K. [4 marks]
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 4
7. Explain the following trend in the lattice energies of the alkali metal hydrides. [4 marks]
latticeH (LiH) = 858 kJ/mole, latticeH (NaH) = 782 kJ/mole, latticeH (KH) = 674 kJ/mole.
8. You are vacationing in Denver Colorado (the 1.6 km high city), and you seem to feel that
the water for your coffee boils faster in Denver than it does in Antigonish NS. Explain. [3
9. What will be the total number of electrons in a shell whose principal quantum number is 4?
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 5
10. What is the concentration in M of an aqueous ethanol solution if 400 mL of that solution
diluted to 4.00 L gives a final concentration of 0.0400 M? [3 marks]
11. How many mL of 0.135 M NaOH would be required to neutralize 13.7 mL of 0.129 M H2SO4?
12. Name the hybrid orbitals that the central carbon atoms in the following molecules would
use? [3 marks]
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 6
13. The critical pressure of CO2 is 73 atm. Is increasing the pressure above Pc a sufficient
condition for the liquefaction of CO2? Explain briefly. [4 marks]
14. What do we mean by a polar molecule? The dipole moments of HCl (g) and HI (g) are 1.08
D and 0.40 D, respectively. which of these molecules will have the [4 marks]
a) greater dipole-dipole interactions;
b) greater dispersion forces?
15. What would be the shape of the AsCl5 molecule? [3 marks]
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 7
Part II - Answer these questions in the space provided. There is limited choice in some
of these questions, so read each question carefully. Show all your work in arriving at the
final answer. Marks are indicated in [ ].
16. Given the following thermodynamic data [9 marks]
H2O2 (g) ⇄ H2O (g) + 1/2 O2 (g)
Substance fH / (kJ/mol) S / (J/K mol)
H2O2 (g) -136.10 232.9
H2O (g) -241.8 188.7
O2 (g) ---- 205.0
a) Will the reaction be spontaneous at 298 K?
b) Will the reaction be spontaneous at 1000 K? Explain briefly.
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17. Draw the Lewis structures for the N2O molecule, showing all resonance structures (hint:
there are three of them!) and formal charges. Predict the shape of the N2O molecule. Using
the concept of the formal charge, which of the three structures is likely to make the most
important contribution to the resonance hybrid? [9 marks]
G. Marangoni Chemistry 100 Summer Session. Final Exam 1998 9
18. DO EITHER A OR B [6 marks]
a) Daff. E. Duck burned 1.50 g of a peanut butter sandwich in a calorimeter where
the heat capacity of the calorineter (Ccal) was 2.76 kJ/C. Given that the
calorineter contained 2000.0 g of water, and that the temperature of the calorimeter
went form 21.36 to 28.78C, calculate the heat of combustion per gram of peanut
butter sandwich. (note s (H2O) = 4.184 J /(g C).
b) The solubility of Ag2SO4 in water is 0.0304 mole/L.
i) Calculate the Ksp of Ag2SO4.
ii) Calculate the solubility of Ag2SO4 in a 1.0 M AgNO3 solution.
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19. DO EITHER A OR B [6 marks]
a) Write the condensed structures for the following compounds.
b) Predict the products of the following reactions
i) CH2 = CH2 + HBr (g)
ii) CH3CH2OH (l) + CH3COOH (l)
iii) C6 H6 (l) + Br2 (l)
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20. DO EITHER A OR B! [8 marks]
a) The equilibrium constant reaction for the anaerobic oxidation of glucose
C6H12O6 (s) ⇄ 2 CH3CH2OH (l) + 2CO2 (g)
is 3.94 x 1039. The conversion of ADP to ATP by the body requires 30 kJ of energy. How
many molecules of ADP can be converted to ATP via anaerobic oxidation?
b) Homer J. Simpson prepares a solution of urea in water that’s 10.0 % by mass urea
(NH2CONH2) at 30.0C
i) Calculate the mole fraction of ethanol in the solution.
ii) Calculate the change in the vapour pressure of water (note P (H2O) = 31.82 torr at
iii) Calculate the number of moles of water in 2.00 L of the vapour at 30.0C.
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21. Ren and Stimpy are asked to prepare a buffer solution by adding solid sodium lactate
(NaC3H5O3) to a 0.200 M solution of the weak acid lactic acid. [6 marks]
a) Calculate the amount of sodium lactate (in grams) that would be needed to prepare a
buffer having a pH of 5.00 (note: assume the volume change on the addition of the
solid is negligible; Ka (lactic acid) = 1.4 x 10-4)
b) Would this buffer have a high capacity to neutralise additional acid or base? Explain
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22. Obtain the orbital diagrams for the following atoms or ions [6 marks]
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1 atm = 760 torr = 101.325 kPa
R = 8.314 J / (K mol) = 0.08206 L atm / (K mol)
Na = 6.022 x 1023 /mol
Planck’s Constant h = 6.6262 x 10-34 J s
Kw = 1.0 x 10-14 at 298.2 K.
molar volume of an ideal gas at STP = 22.414 L
for a quadratic equation ax 2 + bx + c
-b b 2 4ac
quadratic formula x =