Question

A 1.000g sample of benzene (C₆H₆) is burned in a bomb calorimeter whose total heat capacity is 4.957 kJ/ ^oC. If the temperature of the calorimeter increases from 25.30 to 33.74 ^oC , what is the heat of combustion of the benzene per mole.

Explanation please.

Answer 1

1st calculate the heat absorbed by calorimeter

Q = Ccal*delta T

= 4.957 KJ/oC * (33.74 - 25.30) oC

= 41.84 KJ

Molar mass of C6H6 = 6*MM(C) + 6*MM(H)

= 6*12.01 + 6*1.008

= 78.108 g/mol

mass of C6H6 = 1.000 g

we have below equation to be used:

number of mol of C6H6,

n = mass of C6H6/molar mass of C6H6

=(1.000 g)/(78.108 g/mol)

= 1.28*10^-2 mol

heat of combustion = - Q/number of mol

= - 41.84 KJ / (1.28*10^-2 mol)

= -3.27*10^3 KJ/mol

Answer: -3.27*10^3 KJ/mol