Thermodynamics Flashcards
(12 cards)
What happens when work (w) is positive?
Work is done on the system
What happens when work (w) is negative?
Work is done by the system
What is enthalpy?
The sum of a systems internal energy
What is pressure-volume work?
Work done by a gas, and through the expansion and compression of a gas.
- There must be a constant external pressure
- Must see a change in volume for work to be done
When does expansion occur?
- Total volume bigger than 0
- Work less than 0
- Work is done BY the system
- Exothermic
When does compression occur?
- Total volume less than 0
- Work more than 0
- Work done ON the system
- Endothermic
What is Hess’s law?
The total enthalpy change during a reaction is the same whether the reaction occurs via one step or multiple steps
What factors affect entropy?
- Physical state
- Temperature
- Number of particles
- Complexity and size of molecule
What happens when there are less particles?
Less disorder therefore smaller entropy
Why do heavier molecules have a higher entropy?
The number of atoms in the molecule are greater and therefore contributes to higher entropy
What are the units of specific heat capacity?
J/g x celsius
When is a reaction spontaneous?
When free energy is less than zero and total entropy of universe is greater than zero
