Question

Using the following thermochemical equation, determine the amount of heat produced when forming one kg of CO2 during the combustion of benzene (C6H6).

2C6H6(l) + 15O2(g)→12CO2(g) + 6H2O(g)

ΔH°rxn =-6278kJ

Answer 1

Molar mass of CO2,

MM = 1*MM(C) + 2*MM(O)

= 1*12.01 + 2*16.0

= 44.01 g/mol

mass(CO2)= 1 Kg

= 1000.0 g

use:

number of mol of CO2,

n = mass of CO2/molar mass of CO2

=(1*10^3 g)/(44.01 g/mol)

= 22.72 mol

Since Δ H is negative, heat is released

when 12 mol of CO2 reacts, heat released = 6278.0 KJ

So,

for 22.72 mol of CO2, heat released = 22.72*6278.0/12 KJ

= 1.189*10^4 KJ

Answer: 1.19*10^4 KJ