LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

   B.Sc. DEGREE EXAMINATION – CHEMISTRY

FIFTH SEMESTER – NOVEMBER 2010

CH 5507 – PHASE EQUILIBRIA AND KINETICS

 

 

 

Date : 03-11-10                     Dept. No.                                                 Max. : 100 Marks

Time : 9:00 – 12:00

 

PART-A

Answer ALL questions                                                                                            (10 X 2 = 20 marks)

 

• Write the expression for degree of freedom.
• Define Eutectic temperature.
• State Raoult’s law.
• State Nernst distribution law.
• Write the chemical equation for the oxidation of iodide by persulphate. What is the

overall order of the reaction.

• Define specific rate. Comment on its unit.
• A radio active element undergoes nuclear disintegration. What type of complex

reaction is it?

• Predict the effect of added KNO₃ on the rate of oxidation of iodide by persulphate.
• Write the general steps involved in a chain reaction.
• Distinguish between adsorbent and adsorbate.

PART-B

 

Answer any EIGHT questions                                                                                  (8 X 5 = 40 marks)

 

• Draw the phase diagram of sulphur system and apply phase rule to it.
• Magnesium and Zinc form a stable compound with the composition of MgZn₂ having congruent melting point.  Draw the phase diagram for the system and apply phase rule to it.
• (a) Define cryoscopic constant and give its significance.                                    (2)

 

(b) 0.001 Kg of a solute  dissolved in 0.1 Kg of solvent having cryoscopic constant 5.0 K Kg

mole^-1  gave a depression in freezing point as 0.2 K.  Calculate the molecular mass of

the solute.                                                                                                                                (3)

 

• What would be the vapour pressure of 0.5molal solution of urea in water at 298 K. (Given

that vapour pressure of pure water at 298 K is 3173Pa).

 

• Why acid catalysed hydrolysis of ester follows pseudo first order kinetics? Derive the

expression for the rate constant of this reaction.

 

• Describe Van’t Hoff differential method of determining the order of a reaction.

 

• (a) What is critical solution temperature? Explain with an example.                                  (2)

(b) How CST of phenol-water system vary with added NaCℓ ?                                              (3)

 

• In the reaction of hydrogen with bromine under thermal condition, the following observations are made:

1. The rate of the reaction is having first order dependence on H₂ and fractional order dependence on Br₂
2. Product formed, HBr is found to retard the reaction.
3. Presence of radicals is proved.
4. Addition of Br₂ is found to reduce the inhibiting nature of HBr.
5. Overall rate expression for the reaction is rate = {k[H₂][Br₂]^1/2}  {k’ + k”[HBr]}

Propose a probable mechanism for the reaction to explain the above observations.

 

• List any five factors that affect the rate of a chemical reaction.
• Explain Lindemann hypothesis of unimolecular reactions.
• Explain the steps involved in a heterogeneous catalysed reaction.
• Discuss the kinetics of enzyme catalysed reactions.

PART-C

 

Answer any FOUR questions                                                                                  (4 X 10 = 40 marks

 

• Ferric Chloride when added to water, forms four different types of hydrates having definite congruent melting points. Draw a phase diagram depicting the observed phenomenon and apply phase rule to the system.
• (a) Explain the principle of Pattinsons process.                                      (5)

(b) Explain the principle of fractional distillation.                                                                                    (5)

• When 1 liltre of an aqueous solution containing 5g of a solute is shaken with 50 mL of ether, it is found that 0.84 g of solute passes into ether. How much of solute will be left unextracted if same aqueous solution is shaken with second installment of 50 mL ether.  What would be left behind if there was only one extraction with 100 mL of ether.
• (a) Derive the expression for the rate constant of of a second order reaction

2 A products                                                                                                                             (5)

(b) Define half life of a reaction.  How half life measurements can be used to determine the

order of the reaction.                                                                                                                  (5)

27) Give the postulates of collision theory and deduce the expression for the rate constant of

a bimolecular reaction.                                                                                                          (4+6)

28) Derive Langmuir adsorption isotherm equation and explain.                                                     (5+5)

 

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