Page 51 - [B._MURPHY,_C._MURPHY,_B._HATHAWAY]_A_working_meth

Thermodynamics 11 35
(a) AH +ve, AS -ve (b) AH -ve, AS +ve
(c) AH +ve, AS +ve (d) AH -ve, AS -ve
3. How many of the following equations are incorrect?
AU=nCm,,AT AG=RllnK, AU=AH+pAVAH=nC&AT
(a) All four (b) three (c) two (d) one
4. Given that for NH3, AHtap = 23.3 kJ mol-' and AS;,, =
92.2 J K-' mol-', what is the boiling point of NH3 in K?
(a) 21 (b) 525 (c) 293 (d) 253
5. Given that AH,"(FeC12(s)) = -341.8 kJ mol-' and
AH;(FeCl3(,)) = -399.49 kJ mol-', what is AH;, (in
kJ mol- ') for the reaction: FeCl,,,) + 0.5Cl,,,) 4 FeCl,,,)?
(a) -57.7 (b) +714.3 (c) +57.7 (d) 0

LONG QUESTIONS ON CHAPTERS 2 AND 3
1. Use Hess's Law to determine AH;,, for the burning of ethanol
to form carbon dioxide and water, given the following data:
AH;(CH3CH20H(l$ = - 277.7 kJ mol- ', AH,"(C02(g)) =
- 393.5 1 kJ mol- ' and AH;(H20(,)) = - 285.83 kJ mol- '.
2. Determine AG;m for the reaction CHqg) + N2(g)-+HCN(g) + NH3(g)
from the following data:
CH,, N2W HCNW M3(g)
AH,"/kJ mol-' -74.81 0 135 -46.1 1
So/J K-' mol-' 186.15 191.5 201.7 192.3
Comment on the significance of the value of AGK,.
3. Calculate AGR, for the oxidation of B(sl to B203(g, given the
following data:
ow %) B203(s)
AH,"/kJ mol- ' 0 0 - 1272.8
ASo/J K-' mol-' 205.03 5.86 53.97
Comment on the significance of the value of AGkn.