Chemistry Paper IX Physical Chemistry Previous Year Question Paper Year 2005 : IIIrd Year

Q.I. (a) A first order reaction is 15% complete in 20 minutes. How long will it take to be 60% complete ?

(b) Write cell reaction and calculate E° for-the given cell

Image no.3

(c ) When irradiated with light of 5000 Ã… wavelength, 1 x 10-4 mole ofasubstance is decomposed. How many photons are absorbed during the reaction if its quantum efficiency is 10.00

(d) Write down the number of phases, number of components and calculate the degree of freedom for the following equilibrium:
CaCO3(s) – CaO(s) + CO2(g)
Answer :

Q. 2. (a) Enumerate the different methods for determining the order of a reaction. 5
(b) At a certain temperature, the half life period for the decomposition of ammonia in contact with tungsten were as follows:
Pressure (mm of Hg) 50 100 200
Half life period (Relative) 3.52 1.82 ‘ 0.93
Find the order of the reaction,
Answer :

Q. 3. (a) What are concentration cells ? Derive the expression to calculate e.m,f. of a concentration cell without transference. 4
(b) The e.m.f. of the cell
Pb/PbCI2 (s) KCl/Hg2CI2(s)Hg
is 0.5357 V at 298 K and increases with temperature by 1.45 x I0-4 VK-1 Write the cell reaction and calculate ΔG, ΔH, ΔS.
Answer :

Q. 4. (a) What is Lambert’s Law? How has it been extended by Beer ?

(b) When propionaldehyde is irradiated with light of X= 3020 A, it is decomposed to form carbon monoxide.
CH3CH2CHO + hv -> CH3CH3 + CO

The quantum yield for the reaction is 0.54. The light energy absorbed is 15000 erg mol-1 in a given time. Find the amount of carbon monoxide formed in moles in the same time.
Answer :

Q. 5. (a) State the phase rule and define the terms phase, component and degree of freedom by giving examples to illustrate them. 3

(b) Discuss the FeCI3 – H2O system with the help of the phase diagram. Mention the various stable hydrates formed in this system.
Answer :

Q. 6. Write short notes on any two of the following:
(a) Absolute theory of reaction rates;
(b) Applications of Nernst’s distribution law;
(c ) Potentiometric titrations.
Answer :

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