Enthalpy

[bubbles]

I have a couple of things I need help on:

1. How do I calculate the standard enthalpy change for a reaction?

example: 2SO_2 (g) + O_2(g) \rightarrow 2 SO_3(g)

What information do I need to calculate standard enthalpy change? What's the symbol for standard enthalpy change?

Thanks for your help.

[durt]

The symbol is \Delta H^{\circ}. The enthalpy of formation is the enthalpy of the products minus the enthalpy of the reactants. Since the oxygen is in its elemental form its enthalpy is 0, all you need to know are H^{\circ} for SO_2 and SO_3. Don't forget to consider their coefficients.