C + O2 ⟶ CO2 Calculate the enthalpy for the equation above.

Question

I  don't understand enthalpy? could someone help

Answer 1

The answer given by Isaac S. is correct, but you mentioned that you don't understand enthalpy.  For beginning chemistry students, it is easiest to think of enthalpy as the heat of the reaction under constant pressure.  Most (not all) reactions will take place under constant pressure, so just think of enthalpy as "heat".  Heat is a form of energy, so what this question is asking really is "how much heat energy is given off or absorbed when C and O2 react to make CO2.  By convention, the change in enthalpy of formation (∆Hf) is zero for all elements under standard conditions, and in a reaction, ∆H is equal to 

∑∆Hproducts - ∑∆Hreactants.  Thus, as stated by Isaac S., the ∆Hreaction in this question is ∆H CO2 - (∆H C + ∆H O2) which is ∆H CO2 - 0 = ∆H CO2

Answer 2

For this Question the enthalpy will be equal to the Hf of CO2 since the Hf of C and O2  will be 0 because they are elemental