Example: 1.40 g of vegetable oil is placed in a bomb calorimeter with excess oxygen and ignited with a spark. If the calorimeter temperature changes from 20.000 °C to 21.195 °C, find the energy released per gram of oil . The calorimeter contains 2.50 kg of water. The calorimeter without water has a heat capacity of 1.00 kJ°C-1.
















Hess's Law

some properties of enthalpy













Standard States:
















Example: Find the value of DeltaH for the reaction:

2 CO2 + 7 H2 right arrow C2H6 + 4 H2O(g)

From Table find DeltaH values:

Often just list compounds, since known to be from elements.
 C + O2 right arrow CO2  DeltaH = -393.5 kJ mol-1
 2 C + 3 H2 right arrow C2H6  DeltaH = -84.6 kJ mol-1
H2 + 1/2 O2 right arrow H2O(g)  DeltaH = -241.8 kJ mol-1
















Real Gases

van der Waals equations

[Pobs + a(n/V)2] x (V – nb) = nRT























public domain image from Louis E. Keiner via Wikipedia Creative Commons








© R A Paselk

Last modified 6 March 2015