Entropy and Gibbs free energy Flashcards
What does entropy mean?
a measure of the dispersal of energy or disorder of a system. The system becomes energetically more stable when disordered.
It can also be thought of as dispersal of energy from the surroundings to the system or from the system to the surroundings.
What do the surroundings of a reaction include?
- The solvent
- The air around the test tube
- The test tube itself
- anything dipping into the test tube
What is a spontaneous reaction?
They are the changes that tend to happen naturally.
They are usually associated with an increase in entropy.
What is the third law of thermodynamics?
All perfect crystals have the same entropy at a temperature of absolute zero
compare the entropies between:
- Gases, liquids and solids
- Complex and simple compounds
- Harder and softer materials
- As a solid melts
- Gases > Liquids > Solids
- Complex compounds usually have higher entropies than simpler compounds
- Harder compounds usually have lower entropies than softer materials
- As solid melts, its entropy increases
Why do exothermic reactions have a large entropy
The energy can go into rotation and translation, which increases the probability of chemical change.
Why do endothermic reactions have a smaller entropy?
The energy is absorbed from the surroundings, so there is a lesser number of ways of arranging the energy.
What is the difference between a feasible reaction and a non-feasible reaction?
feasible: negative entropy
non-feasible: positive entropy
The formula for entropy change of surroundings?
S(Surroundings) = -H(reaction)/T
-H is the enthalpy change
The formula for the total entropy change?
S(total) = S(system) - H(reaction)/T
Describe entropy in an equilibrium reaction?
At the equilibrium point, the change in enthalpy in the forward reaction is equal to the change of enthalpy in the backward reaction.
What is the expression for Gibb’s free energy?
G = H -T(S)
What is the standard molar Gibbs free energy of formation?
It is the free energy change that accompanies the formation of one mole of a compound from its elements in their standard state.
What is the the standard Gibbs free energy change of reaction?
it is the Gibbs free energy change when the amounts of the reactants shown in the stoichiometric equation react under standard conditions to give products.
