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Sch2108:Organic Chemistry Question Paper

Sch2108:Organic Chemistry

Course:Bachelor Of Science In Public Health

Institution: Meru University Of Science And Technology question papers

Exam Year:2011

INSTRUCTIONS: Answer question one and any other two questions
QUESTION ONE (30 MARKS)
a) i) State and explain types of systems. (6 Marks)
ii) Give the mathematical expression for the total energy of a body and explain the
symbols used. (3 Marks)
b) Show a plot of the pressure of a sample of a gas as a function of volume at constant
temperature. (3 Marks)
c) i) Define Gibbs free energy, G. (2 Marks)
ii) Gibbs free energy may be given as G=H+TS. Explain the meaning of the symbols
H, T and S. (3 Marks)
d) Compound A reacts with compound B to form the products C and D. It is observed
that the rate constant of this reaction is k.
i. Write the rate law for this reaction. (1 Mark)
ii. Experiments on reaction in (i) above show that when the concentration of the
compound A is increased. The reaction rate increases and when the
concentration of compound B is increased, the reaction rate also increases.
What is the order of this reaction? Explain. (2 Marks)
e) i) State Raoult’s Law. (2 Marks)
ii) Explain the term, ideal solution. (2 Marks)
f) i) Using water and ammonia as examples, explain with aid of chemical equations the
BrØnsted – Lowry theory of acids and bases. (4 Marks)
ii) A certain solution contains 1.0 × 102 moles of OH- ions. What is the pH of the
solution? (Kw=[OH-] [H+]=1.0 × 10-14 (2 Marks)
2
QUESTION TWO (20 MARKS)
a) Study the chemical equations given below and predict with reasons whether each of
the following processes involves an increase or decrease in entrophy.
i. The explosive decomposition of NH4NO3
2NH4NO3 (s) 2N2 (g) + 4H2O (g) +O2 (g) (3 Marks)
ii. The conversion of SO2 to SO3
2SO2 (g) + O2 (g) 2SO3(g) (3 Marks)
iii. The extraction of NaCl(s) from sea water
NaCl (aq) NaCl (s) + aq (3 Marks)
iv. The formation of ice from water in a refrigerator
H2O(l) H2O(ice) (3 Marks)
b) Consider the reaction
??2?? ??, ?????? ? ??2?? ??, 1 ?????? ? ?? 0 = 4.07??????????-1 . What is the standard molar
entropy of vaporization of water at 100°??? (4 Marks)
c) Carbon monoxide may be prepared by the reduction of carbon dioxide with carbon
according to the reaction C(s) +CO2(g) ? 2CO(g).
Explain whether the reaction will proceed spontaneously in the FORWARD direction
at 25°??. (4 Marks)
?????
0 ???? = 137.28??????????-1; ?????
0 ????2 = -394.38??????????-1 ?????
0 ???????????????? = 0
QUESTION THREE (20 MARKS)
a) A solution is made of two liquids, the solvent A and solute B, both of which show
tendencies to undergo evaporation. PA and PB are the partial pressures of A and B
while XA and XB are their mole fractions respectively. ????
0 and ????
0 are the vapour
pressure for A and B respectively.
i. Give the expression for the partial pressures for the components A and B.
(4 Marks)
ii. Write the expression for the total pressure PT. (3 Marks)
iii. Give a sketch of a well labeled plot of the vapour pressure of a two-component
system (A&B above) assuming that they form an ideal solution. (6 Marks)
b) A solution contains an equal number of molecules of benzene (C6H6) and toluene
(C7H8). The vapour pressures of benzene and toluene at 25°?? are 95.1 and 28.4
mmHg respectively. calculate
i. The partial vapour pressures of benzene and toluene. (4 Marks)
ii. Total vapour pressures of the solution assuming that it is an ideal solution.
(3 Marks)
QUESTION FOUR (20 MARKS)
a) i) Give Hess’s Law of constant heat summation. (2 Marks)
ii) Given the following thermodynamic equations;
½ N2(g) + ½ O2(g) ??? = 90.37??????????-1
½ N2 (g) +O2(g) NO2(g) ??? = +33.85??????????-1
3
Determine the enthalpy change ??? for the reaction
NO(g) + ½ O2(g) NO2(g) ??? = ? (4 Marks)
b) i) Differentiate between the end point of titration and the equivalence point of a
neutralization reaction. (2 Marks)
ii) What criterion would be taken into account when choosing an indicator for a
titration? (2 Marks)
c) students performed two titration experiments as follows
i. A titration of 0.1M HCL with 0.1M NaOH
ii. A titration of 0.1M NH3(aq) with 0.1M HCI. Sketch the titration curves for
the reactions indicated in (i) and (ii) above. (4 Marks)
d) i) Show the oxidizing and reducing agents in the following reaction.
5????3
2- + 2??????4
- + 6??+ ? 5????4
2- + 2????2+ + 3??2?? (2 Marks)
ii) Calculate the ??0???????? for the voltaic cell given by
????/????2+(0.10??), ????3+(0.20??)¦????2+(0.10??)¦????(??) (4 Marks)
?????????? ????????
????3+ ???? + ??- ? ????2+ ???? ??0 = 0.771??
????+ ???? + ??- ? ???? ?? ??0 = 0.779??

Sch2108:Organic Chemistry Question Paper

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