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 , U , and H .
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) U12
c) w23
d) q23
Q3
P/atm
1
1.00
2
isotherm
T=273 K
3
0.30
22.44
74.80
[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 ƒH for B2H6 (g) .
Ө
(1) B2H6 (g) + 3 O2 (g) → B2O3 (s) + 3 H2O (g)
(2) 2 B (s) + 3/2 O2 (g) → B2O3 (s)
(3) H2 (g) + 1/2 O2 (g) → H2O (g)
Q5
rHӨ = – 1941 kJ mol–1
rHӨ = – 2368 kJ mol–1
rHӨ = – 241.8 kJmol–1
[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)
1
cHӨ = – 7061 kJmol–1
V/L
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 C and 1 atm is
heated to 115 oC . (do not give a numerical answer)
o
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).
ө
b) Calculate ΔrG at 298 K from the standard Gibbs energies of
formation given in the attached table (at 298 K).
2