What is the standard change in enthalpy of formation of #"MgO"(s)#?

The reaction is:

#"Mg"(s) + 1/2 "O"_2(g) -> "MgO"(s)#

1 Answer

The standard enthalpy change of formation, or #DeltaH_f^@#, of magnesium oxide will be -601.6 kJ/mol.


The reaction you're using represents the formation of magnesium oxide from its elements in their most stable forms at standard state, #25^@"C"# and #"1 atm"#.

In the case of formation reactions, the standard enthalpy change of formation for a compound is measured, not calculated; usually, you'll find this value listed either in books or online.


So, in your case, the standard enthalpy change of formation for magnesium oxide was measured to be

#DeltaH_f^@ = "-601.6 kJ/mol"#.

In every day language, the large negative value indicates that this process releases quite a bit of energy as can be observed in the video below.