Test1

Q1 [9 marks]

A sample consisting of 2.00 mol He is expanded isothermally at 22 oC from 22.8 dm3 to 31.7 dm3 (a) reversibly, (b) against a constant external pressure equal to the final pressure of the gas.

For the two processes calculate q, w , DU , and DH .

Q2 [6 marks]

Suppose 1.00 mol of a perfect gas having

CV,m = 12.47 J K–1 mol–1 undergoes

reversible process 1®2®3®1

shown in the figure to the right.

Calculate:

a) The temperature at point 2.

b) DU1®2

c) w2®3

d) q2®3

Q3 [4 marks]

For a reversible adiabatic expansion of an ideal gas, show that

(Tf / Ti)c = (Vi / Vf) where c = CV,m / R .

Start from: dw = – P dV and dU = CV dT

Q4 [3 marks]

From the following data, determine DƒHӨ for B2H6 (g) .

(1) B2H6 (g) + 3 O2 (g) → B2O3 (s) + 3 H2O (g) DrHӨ = – 1941 kJ mol–1

(2) 2 B (s) + 3/2 O2 (g) → B2O3 (s) DrHӨ = – 2368 kJ mol–1

(3) H2 (g) + 1/2 O2 (g) → H2O (g) DrHӨ = – 241.8 kJmol–1

Q5 [4 marks]

When 2.25 mg of anthracene , C14H10 (s), was burned in a bomb calorimeter the temperature roses by 1.35 K. Calculate the calorimeter constant.

Molar mass of anthracene is 172.23 g/mol.

The combustion reaction at 298 K is :

C14H10 (s) + 33/2 O2 (g) → 14 CO2 (g) + 5 H2O (l) DcHӨ = – 7061 kJmol–1

Test 2

Q3. (4 marks)

Calculate ΔS of the system when 2.00 mol of perfect gas with CP,m = 29.1 J K–1 mol–1 undergoes the process :

( Ti = 25 oC , Pi = 1.50 atm ) ( Tf = 135 oC , Pf = 7.00 atm )

Q4. (3 marks)

2.00 mol of perfect gas at 300 K triples its volume in a reversible isothermal expansion. Determine the values of ΔU , ΔH , w , q , ΔS , ΔSsurr , and ΔStot .

Q5. (5 marks)

The volume of 2.00 mol of perfect gas at 300 K increases from 8.55 dm3 to 25.65 dm3 in an isothermal expansion against a constant external pressure of 1.00 atm. Determine the values of ΔU , ΔH , w , q , ΔS , ΔSsurr , and ΔStot.

Q6. (3 marks)

Give an expression to calculate ΔS when one mole of ice at 0 oC and 1 atm is heated to 115 oC . (do not give a numerical answer)

Q7. (4 marks)

Consider the reaction CO (g) + CH3OH (l) → CH3COOH (l)

a) Calculate ΔrGө at 298 K from the standard enthalpies and entropies

given in the attached table (at 298 K).

b) Calculate ΔrGө at 298 K from the standard Gibbs energies of

formation given in the attached table (at 298 K).

1