TOPIC : CHEMICAL THERMODYNAMICS
Number of questions are 180, Select_Question:

QUESTION
Q1) Given
C + 2S → CS2 , ΔHfo=+ 117.0 kJ/mol
C+ O2 → CO2 , ΔHfo=- 393.0 kJ/mol
S+ O2 → SO2 , ΔHfo=- 287.0 kJ/mol
The heat of combustion of
CS2 + 3O2 → CO2 + 2SO2 is ... [ KCET 1994]




SOLUTION

Add equations
C+ O2 → CO2 , ΔHfo=- 393.0 kJ/mol and
2( S+ O2 → SO2 , ΔHfo=- 287.0 kJ/mol)
Resultant is
C+ 2S + 3O2 → CO2 + 2SO2 ( -393 - 2×297=-987 kJ )
By subtracting C + 2S → CS2 , ΔHfo=+ 117.0 kJ/mol from above equation we get
CS2 + 3O2 → CO2 + 2SO2 ( -987 - 117=-1104 kJ /mol)Answer: (b)