Enthalpy and the First Law of Thermodynamics

Table of Contents:

02:10 - Change of internal energy (DE) and molecular motion
02:15 - Changing internal energy - work and heat
04:07 - Signs of heat and work can be - or +
04:51 - Enthalpy (H)
05:52 - State Functions
06:44 - 1. The change in internal energy for the combustion of 1 mol of methane, CH4, in a cylinder is –892.4 kJ. If a piston connected to the cylinder performs 492 kJ of expansion work, how much heat is lost from the system?
08:05 - 2. Suppose that an electric battery drives an electric motor and that the battery and the motor are the system. During a certain period, the motor does 555 kJ of work and the motor and the battery release 124 kJ of heat into the surroundings (perhaps as a result of friction). What is the ΔE of the system?
09:20 - 3. An electric heater operates and absorbs 120,000 J to heat the gas in a cell. The gas expands from 2.0 to 2.5 L against a constant atmospheric pressure of 1.0 atm. What is the change in internal energy of the system in kilojoules?
11:36 - 4. Calculate the work per mole of octane combusted at 298 K when 2.00 mol of octane is burned via this equation: 2 C8H18(l) + 25 O2(g) → 16 CO2(g) + 18 H2O(g).