1 g of graphiteis burnt in a bomb calorimeter in excess of oxygen at 298 K and 1 atmospheric pressure according to the equation C ( graphite ) `+ O_(2)(g) rarr CO_(2)(g)`
During the reaction, temperature rises from 298K to 299 K. If the heat capacity ofthe bomb calorimeter is `20.7 kJ // K `, what is the enthalpy change for the above reaction at 298K and 1 atm ?
During the reaction, temperature rises from 298K to 299 K. If the heat capacity ofthe bomb calorimeter is `20.7 kJ // K `, what is the enthalpy change for the above reaction at 298K and 1 atm ?
Rise in temperature of the calorimeter `= 299- 298K = 1K`
Heat capacity of the calorimeter `= 20.7 k J K^(-1)`
`:. `Heat absorbed by the calorimeter `= C_(v) xxDelta T = (20.7 k J K^(-1)) (1K) = 20.7 kJ`
This s the heat evolved in the combustionof1 g of graphite.
`:. ` Heat evolved inthe combustionof 1 mole of graphite , `i.e., 12g` of graphite `= 20.7 xx 12 kJ = 248.4 kJ`
As this is the heat evolved and the vessel is closed, therefore, enthalpy change of the reaction `( Delta U )`
`= – 248.4 kJ mol^(-1)`