# What is the equation for the calculation of heat of fusion?

##### 1 Answer

Jul 21, 2018

The enthalpy of fusion, **latent heat of fusion**, but it is not the same as

The only "equation" that utilizes

#q_"fus" = pmnDeltaH_"fus"#

#q_"fus"# is theheat flowat constant atmospheric pressure, that pertains to either melting or freezing. Here it is in units of#"kJ"# .#n# is themolsof liquid being freezed, or the mols of solid being melted.#DeltaH_"fus"# is theenthalpy of fusion, and is a positive quantity usually reported in#"kJ/mol"# .

The

#q_"fus" -= q_"melt" = nDeltaH_"fus"#

If one wishes to freeze a liquid...

#q_"fus" -= q_"freeze" = -nDeltaH_"fus"#

And this is because the object is the system... so

- heat flowing in to melt it must be given a positive sign, for the system gains heat to melt.
- heat flowing out to freeze it must be given a negative sign, for the system loses heat to freeze.