When sodium burns in air it produces a bright white light and heat energy

2Na + O2 2Na2O ?H = -414kJ/mol

What would you expect to be the heat energy associated with the reverse process

2Na2O 2Na + O2

Can you please show the entire calculation with units please?

This is what I have but it is wrong:
2 moles Na2O x +414 kJ/mol /2moles Na2O = +828 kJ