Chemistry for Engineers

1

Chemistry for
Engineers POP-up QUIZ Thermodynamics
Name__________________ID___________NANO/ADME/AERO


good luck!
Q1
Q3 For the following processes, decide (and
explain) whether each is expected to be
entropically favourable (DS? ve) or
unfavourable (DS? -ve) ? a) 2Sr(s) O2
(g) 2SrO(s) b) FeCl3(s)
Fe3 (aq) 3Cl- (aq) c) H2 (g)
I2(s) 2HI(g)
negative (ordered salt forms from disordered gas)
positive (ions in fixed salt lattice become
mobile in solution)
cmetal 0.53 J/gK
positive (one mole of gas is converted into 2
moles of gas -disorder increases)
(show working here, 6 marks)
(6 marks)
Q2 From the following thermodynamic
data 2C4H10(g) 13O2(g)
8CO2(g) 10H2O(l) DH? -5760
kJmol-1 C(s) O2(g) CO2(g)
DH? -394 kJmol-1 H2(g)
½O2(g) H2O(l) DH?
-286 kJmol-1 a) What is the value of
DHc?(C4H10) , the molar heat of combustion of
butane? ____________________________________ b)
Use Hess Law to indirectly (from the equations
above) calculate the heat of formation of butane
according to the equation 4C(s) 5H2(g)
C4H10(g) DH? ???
kJmol-1 c) Is the formation of
butane endothermic or exothermic? ________________
________
Q4 a) Given the following heat of formation and
absolute entropy data, calculate DH? and DS? for
the boiling of HCN b) Calculate the
boiling point of HCN (the temperature when liquid
and vapour are in equilibrum)
5760 / 2 2880 kJ/mol
(2 marks)
DHf? (kJmol-1) S?
(JK-1mol-1) HCN (l) 109
113 HCN (g) 135
202
DHvapº (HCN) 26 kJ/mol
DSvapº (HCN) 89 kJ/mol
DHfº (C4H10) -126 kJ/mol
(7 marks)
(3 5 marks)
exothermic
(1 marks)
b.p. (HCN) 292 K (19 ºC)
Total 30 marks