Wednesday 11/2/15 - Hess' Law

In class we did further review of Hess' Law, especially practicing how to use it to solve problems. For example, we had to practice reading a problem and drawing the Hess' Cycle involving various other equations to try and solve the ∆H for the original equation. We also had to read about the laws of thermodynamics, which are useful when learning about enthalpy.

Laws of Thermodynamics:

1. Conservation of energy (energy is neither created nor destroying, merely transferred)
2. Entropy will always increase
3. Reaching absolute zero in temperature (which would also be zero mass and zero motion) is impossible

Additional Review:

∆H for reaction is the same, no matter which route it takes, as long as conditions are the same

∆Hc: ∆H for complete combustion of one mole of a substance with oxygen
∆Hf: ∆H for forming one mole of substance from elements in standard state

Standard conditions: 298K (or just fixed temp.), 1 atm (or 100 KPa), 1M solutions

Bond enthalpy: ∆H to break bonds