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Fst 2109 – Physical Chemistry Question Paper
Fst 2109 – Physical Chemistry
Course:Bachelor Of Science In Food Science And Technology
Institution: Dedan Kimathi University Of Technology question papers
Exam Year:2013
DEDAN KIMATHI UNIVERSITY OF TECHNOLOGY
UNIVERSITY EXAMINATIONS 2012/2013
YEAR ONE SEMESTER II EXAMINATION FOR DEGREE OF BACHELOR OF SCIENCE IN FOOD SCIENCE AND TECHNOLOGY
FST 2109 – PHYSICAL CHEMISTRY
DATE: 23RD APRIL 2013 DATE: 2.00PM – 4.00PM
INSTRUCTIONS: Answer Question ONE and any other TWO questions
Constants: R = 0.082 atm l mol-1 k-1, T (K) = T (?C) + 273
QUESTION ONE (30 MARKS)
a) Define the terms
i. Buffer solution (1 marks)
ii. Azeotropic mixture (1 marks)
b) Distinguish between the following terms
i. Electrolytes and conductors (2 marks)
ii. Charles’ law and Boyle’s law (2 marks)
c) State four important colligative properties exhibited by dilute solutions containing non-volatile solutes. (4 marks)
d) State two causes of deviations of real gases from ideal behaviour. (2 marks)
e) State Le chatelier’s principle (1 marks)
In the reaction N2 + 3H2 ?2NH3 ?H = 92kJmol-1 (3 marks)
i. State how an increase in temperature will affect the yield of ammonia.
ii. State the other two optimum conditions, for the manufacture of ammonia, apart from the temperature.
f) State three main postulates of kinetic theory of gases. (3 marks)
g) i. Define the term solubility product of a binary electrolyte (1 mark)
ii. Calculate the solubility product of lead chloride at 25 ?C given that its solubility at this temperature is 4.75 g litre-1 (Pb = 207, Cl = 35.5) (4 marks)
h) The Van der Waals constant for methane (CH4) are a = 2.25 atm l2 mol-2 and b = 0.043l mol-1. Calculate its critical constants (3 marks)
i) State three characteristics of a chemical equilibrium (3 marks)
QUESTION TWO (20 marks)
a) Write the Ksp expression for the of the following (2 marks)
(i) Ag2CO3 (ii) AgBrO3
b) 100 cm3 of HCl were found to diffuse through a porous plug in 42.5 s, while the same volume of nitrogen compound diffused in 29.3 s under the same conditions. Calculate the relative molecular mass of nitrogen compound (H = 1, N = 14, Cl = 35.5) (3 marks)
c) Two moles of ammonia are confined to a 5-litre flask at 27 ?C. Calculate its pressure using
(i) The gas equation (2 marks)
(ii) The Van der Waals’ equation. (3 marks)
(Given; a = 4.17 atm l2 mol-2, b = 0.0371 lmol-1)
d) Classify the following into Lewis acids and bases: S2-, BF3, Cl-, C2H5OH, (CH3)3N, Ag+ (2 marks)
e) Calculate the volume in ml of a 2.84 M NaOH solution required to titrate 25 ml of 2.25 M H2SO4 (3 marks)
f) i) State Dalton’s law of partial pressure (2 marks)
ii) An enclosed vessel contains 2.8g of nitrogen and 14.2 g of chlorine at 101.3 kpa and 0 ?C. What will be the partial pressure of nitrogen if the temperature is raised to 180 ?C? (3 marks)
QUESTION THREE (20 marks)
a) Distinguish between homogeneous and heterogeneous equilibrium (2 marks)
b) Explain the observation that sodium acetate solution turns litmus blue.
(1 mark)
c) In a titration, 23.8 cm3 of a solution of ethanoic acid (CH3COOH) were neutralized by 25.0cm3 of 0.1059 M sodium hydroxide solution while, in a separate experiment, the acid solution was found to have a pH of 2.86. Calculate the Ka for ethanoic acid (5 marks)
d) The solubility product of BaSO4 in H2O is 1.6 x 10-9 mol2 dm-3. Calculate the solubility in mol dm-3 in pure water (2marks)
e) Using suitable examples, give three common forms of colloidal solutions (3marks)
f) At 267 ?C, 10.425 g of PCl5 are heated in a 4 L flask. The equilibrium mixture had a pressure of 1 atm. Calculate Kp, Kc and ?G? for the reaction at 267 ?C. (P = 31, Cl = 35.5) (4 marks)
g) Calculate the mass of nitrogen gas which exerts a pressure of 2.5x 105 pa in a 300 cm3 vessel at 20 ?C (N = 14, R = 8.31 Jmol-1K-1) (3 marks)
QUESTION FOUR (20 marks)
a) Define the following terms (2 marks)
i. Critical temperature
ii. Critical pressure
b) State Raoult’s law of partial pressure. (1 mark)
c) Distinguish between electrolytic cell and electrochemical cell. (2 marks)
d) 10 g of an impure iron (ii) salt were dissolved in water and made up to 200 cm3 of solution. 20 cm3 of this solution, acidified with dilute H2SO4, required 25 cm3 of 0.04 mol dm-3 KMnO4 solution before a faint colour appeared.
i. Write a balanced ionic equation for the reaction of acidified manganate (vii)/ permanganate ions with iron (ii) ions (3 marks)
ii. How many moles of iron (ii) ions react with one mole of MnO4- ions? (2 marks)
iii.How many grams of Fe2+ are there in the 200 cm3 of the original solution (Fe = 56) (2 marks)
iv.Calculate the percentage by mass of iron in the impure iron (ii)salt (2 marks)
e) NH4Cl aqueous solution turns litmus red. Explain this observation (2 marks)
f) i) What is an “ideal solution” (1 mark)
ii) State the characteristics of an ideal solution (3 marks)
QUESTION FIVE (20 marks)
a) State Avogadro’s law (1 mark)
b) Predict whether there will be any precipitation on mixing 50 ml of 0.001 M NaCl solution with 50 ml of 0.01 M AgNO3 solution. Ksp (AgCl) = 1.5 x 10-10 (4 marks)
c) The solubility product of AgCl is 1.5 x 10-10. What weight of AgCl will be dissolved
i. In 100 ml of water (3 marks)
ii. In a solution containing 0.234 g of NaCl in 100 ml (3 marks)
iii. In a solution containing 0.0.17 g of AgNO3 in 100 ml (3 marks)
d) The dissociation constant of a base at 25 ?C is 1.5 x 10-10. What is
(i) The concentration of hydroxyl ion in 0.015 molar solution of the base (2 marks)
(ii) Its degree of dissociation (2 marks)
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