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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
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DEDAN KIMATHI UNIVERSITY OF TECHNOLOGY UNIVERSITY EXAMINATIONS - 2013/2014 YEAR I SEMESTER II FIRST YEAR SEMESTER II MAIN EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE IN FOOD SCIENCE AND TECHNOLOGY FST 2109 - PHYSICAL CHEMISTRY DATE: 22ND APRIL 2014 TIME: 11.00AM-1.00PM 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 following terms:
i. Partial pressure (1 mark)
ii. Ideal solution (1 mark)
b. Distinguish between the following terms:
i. Systematic approach and Phenomenological approach (2 marks)
ii. Intensive properties and Extensive properties (2 marks)
c. List three characteristics of an ideal solution. (3 marks)
d. State two causes of deviations of real gases from ideal behaviour. (2 marks)
e. State Le chatelier’s principle (1 mark)
i. What will happen to the equilibrium when the temperature of the system is decreased?
N2(g) + O2(g) ? 2NO(g); ?H = 180.5 kJ (1.5 mark)
ii. What will happen to the equilibrium when the volume of the system is decreased?
2SO2(g) + O2(g) ? 2SO3(g) (1.5 mark)
f. State three major assumptions of kinetic theory of gases. (3 marks)
g. i. Define the term solubility product (Ksp) for a sparingly soluble salt (1 mark)
ii. The solubility of calcium fluoride, CaF2 in water is 1.40 x 10-5 mol dm-3 at 298 K. Calculate the solubility products. (2 marks)
iii. State any two applications of solubility products. (2 marks)
h. Calculate the van der Waals constants for C2H6 (ethane) having the critical temperature, Tc (0C) = 32.1, critical pressure, Pc (atm) = 48.8, and critical density, dc (g/cc) = 0.21.
(3 marks)
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i. State four factors without influence on values of equilibrium constant. (4 marks)
QUESTION TWO (20 MARKS)
a. Write the Ksp expression for the of the following (2 marks)
i. Ag3AsO4 ii. CaC2O4
b. An ideal gas occupies a volume of 8.93 litres at 100 0C. What volume will it occupy at 0 0C, the pressure remaining constant (2 marks)
c. 1.5 mole of a certain gas was found to occupy 3 litres at 25 0C. Calculate the pressure that would have been exerted by;
i. Using Van der Waals equation where a = 4.0 L2 atm mol-2 and b = 0.6 L mol-1.
(2 marks)
ii. Using ideal gas equation. (2 marks)
iii. In the light of kinetic molecular theory, explain why there is a difference between the two values. (2 marks)
d. Classify the following: volume, refractive index, enthalpy and specific heat capacity as either intensive or extensive property. (2 marks)
e. Calculate the root mean square velocity of Ozone kept in a closed vessel at 20 ºC and 82 cm mercury pressure. (3 marks)
f. i. State Dalton’s law of partial pressure (2 marks) ii. State and show the mathematical representation of Boyle’s law. Illustrate Boyle’s law using a single graphical representation. (3 marks) QUESTION THREE (20 MARKS)
a. Distinguish between enthalpy of formation and enthalpy of reaction. (2 marks)
b. The hydrogen ion concentration of a fruit juice is 3.3 x 10-2 M. what is the pH of the juice? Is it acidic or basic? (4 marks)
c. State Hess’s law for constant heat summation. (2 marks)
Hydrogen cyanide is a highly poisonous, volatile liquid. It can be prepared by the reaction CH4(g) + NH3(g) ? HCN(g) + 3H2(g) What is the heat of reaction at constant pressure? Use the following thermochemical equations: N2(g) + 3H2(g) ? 2NH3(g); ?H =- 91.8 kJ C(graphite) + 2H2(g) ? CH4(g); ?H = -74.9 kJ H2(g) + 2C(graphite) + N2(g) ?2HCN(g); ?H = 270.3 kJ (4 marks)
d. Estimate the solubility of Ag2CrO4 in pure water if the solubility product constant for silver chromate is 1.1 x 10-12. (2 marks)
e. Using suitable examples, give three common forms of colloidal solutions. (3marks)
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f. You wish to heat water to make coffee. How much heat (in joules) must be used to raise the temperature of 0.180 kg of tap water (enough for one cup of coffee) from 19 0C to 96 0C (near the ideal brewing temperature)? Assume the specific heat is that of pure water, 4.18 J/(g.0C). (2 marks)
g. Under what condition is the enthalpy change equal to the heat of reaction? (1 mark)
QUESTION FOUR (20 MARKS)
a. Define the following terms: (4 marks)
i. Critical temperature
ii. Critical pressure
iii. Cell reaction
iv. Oxidation state
b. State the law of conservation of energy. (2 marks)
c. Distinguish between electrolytic cell and electrochemical cell. (2 marks)
d. Describe the following:
i. A voltaic cell (2 marks)
ii. The function of the salt bridge in a voltaic (galvanic) cell. (2 marks)
e. Draw a standard hydrogen electrode. (3 marks)
f. State the kind of reactions that occur at the anode and the cathode in an electrochemical cell. (2 marks)
g. What is the maximum work you can obtain from 30.0 g of nickel in the following cell when the cell potential is 0.97 V? (Ni = 58.69 g)
Ni(s)|Ni2+(aq)¦Ag+(aq)|Ag(s) (3 marks) QUESTION FIVE (20 MARKS)
a. Define the following terms: (4 marks)
i. pH
ii. Buffer solution
iii. Common-ion effect
iv. Dynamic equilibrium
b. What is the pH of 10-3 M H2SO4? (2 marks)
c. What is meant by end-point of an indicator? (1 marks)
d. State two characteristics of a chemical equilibrium state (2 marks)
e. What is self-ionization? Illustrate using a chemical equation how self-ionization occurs in water. Write the equilibrium-constant expression Kc for the equation. (2 marks)
f. Explain giving reason (s) for the following; water acts as both as an acid and as a base. (4 marks)
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g. Given the cell: Zn(s)/Zn2+(aq)//Cu2+(aq)/Cu(s)
i. Write equations for the reactions at each electrode when the cell produces an electric current? (2 marks)
ii. Explain the charges of the electrodes in (ii) above. (2 marks)
iii. State any two aspects of redox reaction or processes in every day application.
(1 marks)
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