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Sch: 203 Thermodynamics I And Thermochemistry Question Paper
Sch: 203 Thermodynamics I And Thermochemistry
Course:Bachelor Of Science Chemistry
Institution: University Of Nairobi question papers
Exam Year:2012
UNIVERSITY OF NAIROBI
DEPARTMENT OF CHEMISTRY
SCH: 203 THERMODYNAMICS I AND THERMOCHEMISTRY
BSC YEAR TWO: 20112/2013
CAT 1 Time: 1 hour
Date: 6/11/2012
Q1. i)State briefly the thermodynamic meaning of the following terms: system, surrounding
and universe.(3 marks)
ii)Define the first law of thermodynamics and right the differential form of the
law.(2 marks)
Q2. Two moles of a gas at 1 atmosphere and 298K are compressed at constant temperature
by use of a constant pressure of 5 atm.
i). Calculate the work done on the gas.(2 marks)
ii). If the compression is driven by 10kg gas mass, how far will the mass fall in earth as gravitational field (R= 8.3145JK-1 , g= 9.8 ms-1) (2 marks)
iii). A system expands from an initial volume of 1.0 L to 4.0 L against a pressure of 10 atm. Calculate the work done in joules (1 L- atm = 101.325 J). (2 marks)
Q3. From the equation change in E = change in H – P change in V, the value of work change in V is negative hence change in E will be greater than change in H. For any reaction that consumes more moles of gas than it produces the value of change in H will be negative. Based on this argument, determine which of the reactions given below will have the value of change in E greater than that of change in H. Give an explanation for the choice. (4 marks)
i). CaCN2 (S) + 3H20(l) = Ca CO3 (s) + 2NH3 (g)
ii). 3H2 (g) + N2 (g) = 2NH3 (g)
iii).UO2 (s) + 4HF (l) = UF3 (S) + 2H2O(l)
iv). H2 (g) + I2 (g) = 2HI (g)
Q4. i). Differentiate between isothermal and adiabatic process. (1 mark)
ii). Consider isocoric (change in V= 0) in which the pressure of a 2.35 mole sample of ideal gas changes from 1.60 atm at 197K to 2.70 atm. The final temperature during the change is 332K and CV for the gas is 3/2R. Calculate q, w, change in E, and change in H for the process (R=8.314J/ 0C/mol, 1 atm= 101.325 J) (7 marks)
Q5. i) Write the expression for the internal pressure of an ideal gas and give a reason why its value equals zero. (2 marks)
ii) Differentiate between molar heat capacity and specific heat of a substance (2 marks)
iii) A sample of titanium is heated with an electric coil. If 102 joules of energy are added to a 12.4 g sample and the final temperature is 37.20C , calculate the initial temperature of the titanium. Heat capacity of titanium is 0.523 J/g0C (3 marks)
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