PHYSICAL CHEMISTRY (A);EXAM
ID Number Total Points
Tuesday July 11th 2006 Time: 110 Minutes 100 points total
Number 1 2 3 4 5 6 7 8 9 10 Total
Answer all questions in detail and SHOW ALL WORK!
Please write answers on your answer-paper.
1. To select the best answer (10pts)
(1). (2 pts) A bomb calorimeter (i.e.like the one I brought to class) measures ( )
a. the work done by the system at constant volume. b. the work done by the system at constant pressure. c. the heat released by the system at constant volume. d. the heat released by the system at constant pressure.
(2). (2 pts) Which of the following is not one of the Laws of Thermodynamics. ( )
a. The entropy at 0，C is zero.
b. For an isolated system a spontaneous process results in an increase of the entropy
of the system.
c. The entropy of the universe increases.
d. ;E = q +w
(3). (2 pts) If the first Law of Thermodynamics is stated as ;E = q - w, which of the
following statements is true? ( )
a. For w > 0, this represents work done by the system.
b. For q >0, this represents heat released by the system. c. For w > 0, this represents work done on the system.
d. None of the above.
(4). (2 pts) Which of the following is false with regards to a state function? ( )
a. Changes in state functions only depend on the initial and final states. b. Enthalpy is a state function.
c. Heat at constant pressure may be considered a state function d. Entropy is a state function
e. Work is a state function.
(5) (2 pts) There is a spontaneous process carrying out in a closed system: ( )
-1-1a. ;S> 0 J.mol.K sys.
-1-1b. ;S< 0 J.mol.K sys.
-1-1c. ;S= 0 J.mol.K sys.
d. None of the above.
2 .Match the best description from the right column with the formula from the left column (there is only one best match) (10 pts)
3. (15pts)Thermodynamics: As it was known thermodynamic data for all compounds at 298.15 K, 1 bar
；-1(1) (5pts) Determine ;H (298.15 K ) of the following reaction in kJ mol r
(COOH) (s) + ? O(g) ？ 2CO(g) + HO(l) 2222
；-1 (2) (5pts) Compute ;H (298.15 K ) kJ molfor reaction: r
(COOH) (s) + H(g) ？ 2 HCOOH (l) 22
Based on the following reactions:
(COOH)2 (s) + ? O(g) ？ 2CO(g) + HO(l) 222
HCOOH (l) + ? O(g) ？ CO(g) + HO(l) 222
H(g) + ? O(g) ？H2O(l) 22
；(3) (5pts) Using part b’s answer, determine the ;H in kJ for
(COOH) (s) + H(g) ？ 2 HCOOH (l) if 276.18 g of HCOOH (l) is produced. 22
4. (10pts) Thermodynamics: Thermal decomposition of calcium carbonate (calcite)
proceeds according to the following reaction:
Calculate the pressure of CO at equilibrium with solid calcium carbonate and 2
calcium oxide at 1500 K.
；-1；-1( ;G (298.15K,CaCO): -1128.79 kJ mol; ;G (298.15K,CaO): -604.03kJ mol; f3f
；-1-1-1;G (298.15K,CO): -394.359kJ mol; ;C！ 0 kJ molK) f2P.
5. (15 pts) Chemical kinetics:
(1) (5pts) Outline the assumptions made in the steady state approximation when
applied to chemical rate laws. Your answer should make reference to the rates of
the individual elementary reactions and the time dependence of reactant and
(2) (10pts) :
Assuming that steady state conditions apply, show that the reaction obeys the following rate law:
6. (15 pts) Electrochemistry:
(1) (5pts) What is meant by a standard electrode potential? Discuss the use of such quantities.
；pts) E(2) (10 for the cell Pt(s) ，H (g) ，HCl(aq) ，Hg Cl (s) Hg(l) is +0.2699 V at 222
293 K and +0.2669 V at 303 K:
(i) Write down the cell equation
；；(ii) Calculate ;rS, ;rHand the equilibrium constant K at 298 K.
7. (15 pts) Surfaces:
(1) (5pts) The principal features of chemisorption are expected to be well described by the Langmuir adsorption isotherm
where P is the pressure of the gas and K is independent of pressure. Derive this equation, stating clearly the assumptions on which it is based. Why does the Langmuir isotherm fail to describe the characteristics of physisorption? (2) (10pts) Carbon monoxide is found to adsorb on the (111) surface of a particular transition metal single crystal. N, the number of CO molecules adsorbed per square metre, is measured as a function of CO gas pressure, PCO, at 400K. The results are
presented in the table below:
Show that the data conform to the Langmuir isotherm equation (1) above. Calculate the values for K and for N, the maximum surface concentration of CO ？
which can be chemisorbed.
8. (10pts) Solutions:
Two pure liquids A and B form an ideal solution when mixed together. (1) Describe how the partial vapour pressures of the two substances in the mixture will vary with changes in mixture composition and show their chemical potentials. (2) Calculate values for the Gibbs energy and entropy of mixing at 298 K when x = 0.75. B