What is the difference between....?

Question

heat of formation and heat of combustion??
are they the same thing?

Answer 1

No. Heat of formation is for all compounds, which can be negative. Heat of combustion is only for compounds with Oxygen in it, and it has to be positive.

Hope this help : )

Answer 2

The Heat of combustion (ΔcH0) is the energy released as heat when a compound undergoes complete combustion with oxygen. The chemical reaction is typically a hydrocarbon reacting with oxygen to form carbon dioxide, water and heat. It may be expressed with the units;

The standard enthalpy of formation or "standard heat of formation" of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 100 kPa of pressure and the specified temperature, usually 298 K or 25 degrees Celsius). Its symbol is ΔHfO.

For example, the standard enthalpy of formation of carbon dioxide would be the enthalpy of the following reaction under the conditions above:

C(s,graphite) + O2(g) → CO2(g)

There's a lot more explications and graphs on the web site (source)

Answer 3

Heat of formation is what is meant by the word, forming the compound.

Heat of combustion is the heat involved in the reaction of the compound with oxygen.

Answer 4

The standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states

The heat of combustion of a compound is the energy released as heat when the compound undergoes complete combustion with oxygen.