For a state function, depends only on the starting and ending states

Solving for $\Delta H$

Types of problems

1. Calorimetry (9/10)
2. Adding Reactions (9/10)
3. “Heat of Formation” Values (9/11)
4. Bond Energy (Q2)
5. From Gibbs Energy (Q4)

Examples (Adding Reactions)

• This is logically just Systems of equations, manipulating an equations to get things to cancel!

Goal:

$H_2SO_4~{(L)}$→$SO_3~{(g)} + H_2O~_{(g)}$

Given Reactions:

$H_2S~{(g)} + 2O_2~{(g)}$ → $H_2SO_4~_{(L)}$ $\Delta H = -235.5~\frac {Kj} {mol}$

$H_2S~{(g)} + 2O_2~{(g)}$ → $SO_3~{(g)} + H_2O~{(L)}$ $\Delta H = -207 \frac {Kj} {mol}$

$H_2O~{(L)}$ → $H_2O~{(g)}$ $\Delta H = 44 \frac {Kj} {mol}$

How To

• To get to the goal reaction we have to make the parts of the reactions cancel, by this I mean that the reactants cancel with the products
• You always want to start with a reactant or product that isn’t in the other reactions