Chemistry - DrBob222
posted by Timofey .
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
If it is -414 kJ/mol going in the forward direction it must be +414 kJ/mol going in the opposite direction.
the enthalpy -414kJ/mol is the enthalpy of combustion. i.e. how much energy released for one mole of Na metal to burn in air. so the actual equation is;
Na + 1/2O2 --> NaO ?H = -414kJ/mol.
However, the equation given in your question is written in whole number coefficients just to get rid of the 1/2 but keep in mind that the ?H still remain the same in this case.
so simply reverse the sign