Question

For gas 'A' in a calorimeter heat evolved is 250 kJ/mol. For 0.2 mol of A, temperature rise from 298 K to 300K. Find out heat capacity of calorimeter -
(1) 12.5 kJ/K
(2) 25 kJ/K
(3) 50 kJ/K
(4) 100 kJ/K

Answer 1

For 1 mole ∆E = 250 kj/mol For 0.2 mole ∆E = 250 ×0.2 = 50kj /mol On giving 50kj heat ∆T=2 2---->50 For temp rise of 1 ( heat capacity ) 1----->25

Answer 2

Answer : (2) The heat capacity of calorimeter is 25 kJ/K.

Solution : Given,

Heat evolved = 250 kJ/mole

Number of moles = 0.2 mole

Initial temperature = 298 K

Final temperature = 300 K

Formula used :

$Q=n\times C\times \Delta T$

where,

Q = Heat evolved

n = Number of moles

C = Heat capacity

$\Delta T$ = $(T_{final}-T_{initial})$ =Change in temperature

For 1 mole heat evolved is 250kJ/mole

For 0.2 mole heat evolved is 250kJ/mole × 0.2mole = 50 kJ

The heat evolved, Q = 50 kJ

$\Delta T$ = $(T_{final}-T_{initial})$ = 300 - 298 = 2 K

Now put all the values in above formula, we get the heat capacity.

$50kJ=1\times C\times 2K$

C = 25 kJ/K

Therefore, the heat capacity of calorimeter is 25 kJ/K.