Chemistry

Enthalpy (continued)


Enthalpy of combustion

It is always an exothermic reaction.

It is the heat released in the combustion reaction of 1 mol of a substance in the presence of oxygen gas O2(g)

Complete combustion: more amount of oxygen. Forms carbon dioxide and water.

Incomplete Combustion: less amount of oxygen. Produces less amount of energy. Forms more waste like carbon monoxide (CO) and water (H2O).

Example:
What is the value of the enthalpy of combustion of benzene (C6H6)? Dice:


Table of ΔH ° comb of some substances

Substance

Formula

ΔH ° comb (kcal / mol)

Hydrogen

H2(g)

-68,3

Carbon graphite

C (graphite)

-94,1

Carbon monoxide

CO (g)

-67,6

Methane

CH4(g)

-212,8

Ethane

Ç2H6(g)

-372,8

Propane

Ç3H8(g)

-530,6

Butane

Ç4H10(g)

-688,0

Benzene

Ç6H6(g)

-781,0

Ethanol

H3C - CH2 - OH (l)

-326,5

Acetic Acid

H3C - COOH (1)

-208,5

Glucose

Ç6H12O6(S)

-673,0

Sucrose

Ç12H22O11(S)

-1348,9