1 g of graphiteis burnt in a bombcalorimeter in excess of oxygen at 298 K and 1 atmosphericpressure accordingto the equation C ( graphite ) + O_(2)(g) rarr CO_(2)(g) During the reaction, temperature rises from298K 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 ?

1 g of graphiteis burnt in a bombcalorimeter in excess of oxygen at 29

1.	1 g of graphiteis burnt in a bombcalorimeter in excess of oxygen at 298 K and 1 atmosphericpressure accordingto the equation C ( graphite ) + O_(2)(g) rarr CO_(2)(g) During the reaction, temperature rises from298K 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 ?
Answer» Solution :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)`