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Physical Chemistry Ii Supplementary Question Paper

Physical Chemistry Ii Supplementary

Course:Bachelor Of Science In Analytical Chemistry

Institution: Jomo Kenyatta University Of Agriculture And Technology question papers

Exam Year:2009

SECOND YEAR SPECIAL/SUPPLEMENTARY EXAMINATION FOR THE DEGREE OF BECHELOR OF SCIENCE.
SCH 2201:PHYSICAL CHEMISTRY II.
DATE: MARCH 2009 TIME:2HRS.
Instructions: Answer question ONE and any other TWO questions.
Useful universal constants:
R=8.314JK-1mol-1 = 8.205 × 10-2 atmK-1mol-1
C=3.0 × 108 m/s
NA=6.023 × 1023 mol-1
1 Torr=1.33 × 102 Nm-2
1 bar =1.0 × 105 NM-2
QUESTION ONE (30 MARKS).
A)Explain, with the examples where possible, the following:
i)work (2mrks)
ii)heat (2mrks)
iii)Bohr Temperture (2mrks)
iv)Order of a reaction(2mrks)
v)reaction mechanism (2mrks)
B)i)Explain why real gases deviate from ideal gas behavior (3mrks)
ii)State the principle of corresponding states.(1mrk)
iii)Estimate the critical constants of a gas with van der waals paremeters a= 0.751 atm L2mol-2 and b=0.0226 Lmol-1(3mrks)
C(i)Explain what is internal energy (U).
(ii) A mole of monoatomic gas at 1 bar and 273.15K is allowed to expand adiabatically against a constant pressure of 0.395 bar until equilibrium (CV =3/2 R)
a)Calculate the final volume.(2mrks)
b) Calculate the final temperature.(2mrks)
c)calculate the work done during the process.(2mrks).
D)(i) Consider the reaction
A + B ? products
From the following data at a given temperature determine the order and rate constant of the reaction: (4mrks)
(A)mol dm-3 (B)mol dm-3 rate(mol-1)
1.5 1.50 3.2 × 10-1
1.5 2.50 3.2 × 10-1
3.0 1.50 6.4 × 10-1
ii) The rate constant for the second order reaction:
2NO2(g) + 2NO(g) + O2(g) is 0.54Ms at 30oC
Calculate how long it will take for the concentration of NO2 to decrease from 0.62M to 0.28M (mrks)
Question two
A)Explain three methods for determining the rate law.
B)The data for determining 2A ?A2? of a certain reaction in ethanol solution at 40oC is as follows:
(A)moldm-3 × 10-3 68 50.2 40.3 33.1 28.4 22.3 18.7 14.5
(t)/Min 0 40 80 120 160 240 300 420
Using half life method , determine the reaction order.
C) (i) Explain A and Ea factors in the Arrhenius equation.(2mrks)
Question three A)Consider the reaction
A?B.
The rate of reaction is 1.6 × 10-2 M/s when the concentration of A is 0.35M. Calculate the rate constant if the reaction is
i)first order in A(2mrks)
ii)second order in A(2mrks)
B)(i) Define half-life (1/2)
(ii) write the equation relating the half life of a first –order reaction to the rate constant.(4mrks)
(iii)for a first-order reaction , how long will it take for the concentration of reaction to fall to one-eight its original value?(write your answer in terms of K)
(C) Variation of the rate constant with temperature for the first order reaction
2N2O5(g)? 2N2O4(g) + O2(g)
Is given in the following table. Determine graphically the activation energy for the reaction.(8mrks)
T(K) K(s-1)
298 1.74× 10-5
308 6.61× 10-5
318 2.51 ×10-4
328 7.59 × 10-4
338 2.40 × 10-3
(D) The rate of decomposition of a zomethane is studied by monitoring the partial pressure of the reaction as a function of time:
CH3-N=N-CH3(g)? N2(g) + C2 H6(g)
The data obtained at 300oC are shown in the following table:
Time(s) partial pressure of Azomethane(mmHg)
284
100 220
150 193
200 170
250 150
300 132
Use the integrated first-order rate law to show that these values are consistent with first order kinetics and determine the rate constant(6 mrks).
Question four
(A)(i) List three main differences between real gases and ideal gases (3 marks)
(ii)State the principle of corresponding states.(1 mrk)
(B) For ethane, Pc=48.2 atm and Tc=305.4K. calculate the pressure exerted by 74.8g of C2H6 in a 200 cm3 vessel at 37.5OC using
i)the ideal gas law .(3mrks)
ii)the van der waals equation (4mrks)
iii)comment on the values from (i) and (ii) (1 mrk)
(C) use the virial equation of state to show that for a real gas ;
lim-(P?o)?¦((?-?id)@)=B(T) (3mrks)
(D)Calculate z from the van der waals equation with a =5.464 L2 atm mol-2 and b=0.03049Lmol-1 at 776.4K for water vapour at 327.6 atm given that its density is 133.2gL-1.

Physical Chemistry Ii Supplementary Question Paper

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