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Chemistry for Engineers
POP-up QUIZ : Thermodynamics
Name__________________ID___________NANO/ADME/AERO
good
luck!
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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)
negative (ordered salt forms from
disordered gas)
b) FeCl3(s)
Fe3+ (aq) + 3Cl- (aq)
positive (ions in fixed salt lattice
become mobile in solution)
cmetal = 0.53 J/g·K
(show working here, 6 marks)
c) H2 (g) + I2(s)
2HI(g)
positive (one mole of gas is
converted into 2 moles of gas
-disorder increases)
(6 marks)
Q2: From the following thermodynamic data:
2C4H10(g) + 13O2(g)
C(s)
+ O2(g)
H2(g)
+ ½O2(g)
8CO2(g) + 10H2O(l) DH = -5760 kJmol-1
CO2(g)
DH = -394 kJmol-1
H2O(l)
DH = -286 kJmol-1
a) What is the value of DHc(C4H10) , the molar heat of combustion
(2 marks)
5760 / 2 = 2880 kJ/mol
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
Q4: a) Given the following heat
of formation and absolute entropy
data, calculate DH and DS for
the boiling of HCN
DHf (kJmol-1)
HCN (l)
HCN (g)
+109
+135
S (JK-1mol-1)
113
202
DHvapº (HCN) = +26 kJ/mol
DSvapº (HCN) = +89 kJ/mol
DHfº (C4H10) = -126 kJ/mol
(7 marks)
b) Calculate the boiling point of
HCN (the temperature when
liquid and vapour are in
equilibrum)
(3+ 5 marks)
c) Is the formation of butane endothermic or exothermic?
________________________
exothermic
(1 marks)
b.p. (HCN) = 292 K (19 ºC)
Total: 30 marks