Chemical Thermodynamics Question 471
Question: A 1 g sample of octane $ C_8H_{18} $ is burned in excess of oxygen in a bomb calorimeter. The temperature of the calorimeter rises from 294 K to 300 K. If heat capacity of the calorimeter is 8 kJ/K, the enthalpy of combustion of octane is
Options:
A) 5472 kJ/mol
B) 48 kJ/mol
C) 684 kJ/mol
D) 4281 kJ/mol
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Answer:
Correct Answer: A
Solution:
- Rise in temperature = 300 - 294 = 6 K Heat given to the calorimeter = Heat capacity $ \times ,\Delta T $
$ =8\times 6 $
= 48 kJ Molar mass of octane $ (C_8H_{18})=114 $
1 g of octane gives = 48 kJ heat 114 g of octane = 1 mol of octane gives $ =48\times 114kJ $
= 5472 kJ/mol
