How are enthalpy changes expressed in chemical equations?
The enthalpy change for a given reaction depends on the stoichiometry of the reaction.
For example, 2 mol of carbon monoxide react with 2 mol of nitrogen monoxide according to the balanced equation:
The process is exothermic, releasing 746 kJ of energy. This amounts to 373 kJ of energy per mole of
Consider now the reaction of 0.250 mol carbon monoxide.
We can calculate the amount of energy released by using the enthalpy of reaction (
Therefore, a change in enthalpy
The reaction of 0.250 mol of
Now consider the reaction
a) What is the enthalpy change for the formation of one mole of nitrogen monoxide?
Here we use the conversion factor
b) What is the enthalpy change for the reaction of 100.0 g of nitrogen with excess oxygen?
Here, we need to convert grams of