Chapter: 11th Chemistry : UNIT 7 : Thermodynamics
Solved Example Problem: Second Law of thermodynamics
Problem: 7.10
If an automobile engine burns petrol at a temperature of 816o C and if the surrounding temperature is 21o C, calculate its maximum possible efficiency.
Solution:
Here
Th = 816+273= 1089 K;
Tc= 21+273= 294K
%Efficiency=( 1089-294 / 1089) x100
%Efficiency=73%
Problem: 7.6
Calculate the standard entropy change for the following reaction( ∆S0f ), given the standard entropies of CO2(g), C(s),O2(g) as 213.6 , 5.740 and 205 JK−1 respectively.
C(g) + O2(g) →CO2(g)
S0r = ∑ S0products − ∑ Sreac0 tan ts
S0r = {S0CO 2 } − {SC0 + S0O2 }
S0r = 213.6 − [5.74 + 205]
S0r = 213.6 −[210.74]
S0r = 2.86 JK−1
Problem: 7.7
Calculate the entropy change during the melting of one mole of ice into water at 00 C and 1 atm pressure. Enthalpy of fusion of ice is 6008 J mol-1
Given:
∆Hfusion = 6008 Jmol−1
Tf = 0 0
C = 273 K
H 2O(S) --273 K→ H 2O ( l)
S fusion = 22 .007 J K −1 mole−1
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