Question

The temperature rises from 25.00°C to 29.00°C in a bomb calorimeter when 3.50 g of sucrose undergoes combustion in a bomb calorimeter. Calculate ΔE rxn for the combustion of sucrose in kJ/mol sucrose. The heat capacity of the calorimeter is 4.90 kJ/°C. The molar mass of sugar is 342.3 g/mol.

Answer 1

Answer: Hence the energy change is -1918 kJ/mol

Given:

Initial temperature of calorimeter T1 = 25 C

Final temperature T2 = 29 C

Heat capacity of calorimeter c = 4.90 kJ/C

Mass of sucrose (m) = 3.5 g

Molar mass of sucrose (M) = 342.3 g/mol

To determine:

The energy change for the combustion of sucrose in kJ/mol

Explanation:

The change in temperature of calorimeter = T2 -T1 = 29 - 25 = 4 C

Heat gained by the calorimeter when the temperature changes by 4 C is-

= 4 C * 4.90 kJ/ 1 C = 19. 6 kJ

Now,

Heat gained by calorimeter = heat lost during combustion of 3.5 g sucrose = -19.6 kJ

# moles of sucrose = 3.5 g/342.3 g.mole-1 = 0.01022 moles

Energy change for the combustion reaction = -19.6/0.01022 = -1917.8 kJ/mol