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Chem 221: Gases And Phase Equilibria Question Paper
Chem 221: Gases And Phase Equilibria
Course:Gases And Phase Equilibria
Institution: Egerton University question papers
Exam Year:2016
Useful Data:
Gas constant, R= 0.08206L.atm/mol.K
K-1 = 8.314J/mol.K
1J=1kg/m2.S
Atomic Masses: H=1,He=4,C=12,O=16,K=39
QUESTION ONE
(a) (i) Derive the kinetic gas equation: PV=1/3MnU2
(ii) Use the kinetic gas equation to deduce Charles'' law
(b) The compressibility factor Z can be used as a measure of deviation of a gas from ideal behavior:
(i) sketch on the same axes the graphs of Z against pressure for H, He, CO2 and an ideal gas
(ii) Give a reason for abnormal behavior of CO2
(c) The energy difference between the vibration energy modes is about 10kJ/mol. Calculate the ratio of gas molecules undergoing vibration at 298K using the Boltzmann distribution.
QUESTION TWO.
(a) (i) Sketch the curves for the Maxwell-Boltzmann distribution of a gas at three different temperatures, viz 273K,373K and 1500K.
(ii) Calculate the most probable velocity and the mean velocity of He gas at 298K
(b) Draw a well labelled diagram of the P-V isotherms of CO2 gas obtained by T. Andrews
(c) The values of critical constants for hydrogen gas are:
V=65cm3/mol P=13atm T=33K
(i) calculate the values of the Van Der Waal''s constants a and b
(ii) Evaluate the value of the compressibility factor of the gas at the critical point
QUESTION THREE
(a) A 10g sample of potassium ethanoate is dissolved in 250ml 0f solution:
(i) Derive the expression for obtaining the pH of this solution
(ii) Calculate the hydrolysis constant
(iii) Calculate the degree of hydrolysis
(iv) Calculate the pH of the solution
(b) The minimum concentration of oxygen in water required to support life is 4mg/l. Calculate:
(i) The mole fraction of oxygen in 1litre of this water
(ii) Hence determine the partial pressure of oxygen in water(Henry''s law constant, Kh=43,421atm
QUESTION FOUR
(a) Define an ideal solution
(b) Liquid C and D form an ideal solution. When 1mole of C and 3moles of D are mixed, the resulting solution has vapour pressure of 12,600N/m2 at 293K. If the vapour pressure of pure D is 13,200N/m2, calculate the mole fraction composition of the vapour in equilibrium with the above solution.
(c) Calculate the number of degrees of freedom at the triple point of water
(d) The vapour pressure of 500g of sample of benzene was 0.526atm at 333.6K but fell to 0.508atm when 19g of non-volatile organic compound was dissolved in it. Calculate the molar mass of the compound.
(e) When 13.86g of solute (molecular mass=154) is added to 100g of benzene, the boiling point of the solution is 355.3K. Given that the boiling point of pure benzene is 353.0K, calculate:
(i) the ebullioscopic constant of benzene
(ii) the molar heat of vaporization of benzene
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