Question

A 12.6-g sample of acetylene, C₂H₂, produced a tempera- ture increase of 16.98c in the same calorimeter. what is the energy of combustion of acetylene (in kj/mol)?

Answer 1

The energy of combustion of acetylene (C2H2) is -231.3 kJ/mol.

To find the energy of combustion of acetylene (C2H2) in kJ/mol, use the formula ΔE = mcΔT to calculate the energy change, then determine the energy of combustion (ΔHc = -ΔE), and finally calculate the molar energy of combustion by dividing ΔHc by the number of moles of acetylene.

The given information is:

Mass of acetylene sample: 12.6 g

Temperature change: 16.98°C

Specific heat capacity of the calorimeter: 1.9 J/g°C

(a) Calculate the energy change (ΔE):

ΔE=mcΔT

ΔE=(12.6 g)(1.9 J/g°C)(16.98°C)

ΔE=231.3 J

(b) Calculate the energy of combustion (ΔHc):

ΔE= −Δ
`H_(c)`

Δ
`H_(c)`= −ΔE

Δ
`H_(c)`= −231.3 J

(c) Calculate the molar energy of combustion:

Molar energy of combustion= Δ
`H_(c)` / moles of acetylene

Molar energy of combustion=
`(-231.3 J)/(1 mol)`

Molar energy of combustion=−231.3 kJ/mol

Therefore, the energy of combustion of acetylene (C2H2) is -231.3 kJ/mol.