1. Mg(s) + ½ O2(g)  MgO(s) H = ? kJ/mol
Thermochemistry Lab Calculations
Goal: What is H for the formation of MgO from Mg(s) and O2(g)?
Mg(s) + ½ O2(g)  MgO(s) H = ? kJ/mol
Data:
From lab measurements:
Mg(s) + 2 H+(aq)  Mg2+(aq) + H2(g) H1 = ___________ kJ/mol
MgO(s) + 2 H+(aq)  Mg2+(aq) + H2O(l) H2 = ___________ kJ/mol
From a table: H2(g) + ½ O2(g)  H2O(l) H3 = kJ/mol
Task: Find a way to add these three reactions to get the desired reaction. Manipulate the H values as needed, and add them.

3. Given:
Pb(s) + PbO2(s) + 2H2SO4(l) → 2PbSO4(s) + 2H2O(l); ∆H° = –509.2 kJ
SO3(g) + H2O(l) → H2SO4(l); ∆H° = –130. kJ
determine ∆H° for the following thermochemical equation.
Pb(s) + PbO2(s) + 2SO3(g) → 2PbSO4(s)
a) –3.77 × 103 kJ
b) 3.77 × 103 kJ
c) –639 kJ
d) –521 kJ
e) –769 kJ

4. Calculating Heat Production

5. Heat of Formation

6. Heat of Formation: The general idea

8. Find the enthalpy change for burning ethyl alcohol

9. What is the standard enthalpy change for the following reaction?
N2H4(l) + 2NO2(g) → 2N2O(g) + 2H2O(l)
a) –119.7 kJ
b) –290.6 kJ
c) kJ
d) –524.2 kJ
e) kJ
Substance
∆H°f (kJ/mol)
N2H4(l)
+50.6
NO2(g)
+33.1
N2O(g)
+82.1
H2O(l)
–285.8