The heat capacity of a certain bomb calorimeter is 8.75 kJ/degree C. That is, it
ID: 494150 • Letter: T
Question
The heat capacity of a certain bomb calorimeter is 8.75 kJ/degree C. That is, it takes 8.75 kJ of energy to raise the temperature of the assembly 1.00 degree C. 10.0 grams of (C_2H_5NO_2) is burned inside the bomb calorimeter at initial temperature of 25.0 degree C. At the end of the reaction the temperature in the calorimeter has risen to 40.0 degree C. Calculate the enthalpy change for the combustion of as shown below. (You may ignore changes in pressure inside the calorimeter) 4 C_2H_5NO_2 (s) + 9 O_2 (g) rightarrow 8 CO_2 (g) + 10 H_2O (g) + 2 N_2 (g) delta H degree = ?Explanation / Answer
The heat given by combustion of glycine = heat absorbed by calorimeter
heat absorbed by caorimeter = heat capcity x difference in temperature
= 8.75 c x (40-25)
= 131.25 kJ
And the heat given by glycine = - 131.25 kJ
when 10 gof glycine is burnt , we get -131.25 kJ of heat
one mol (75g/mol) of glycine can give heat =
heat = -75g/mol x 131.25 kJ /10g
= -9843.75 kJ/mol
As per the given equation (ignoring the pressure changes),4 moles of glycine are burnt
the heat given will be = -4 x9843.75 kJ/mol
= 39375 kJ
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