Entropy Flashcards
1
Q
Spontaneous reaction
A
- once started
- can continue on its own without input of energy
2
Q
Non-spontaneous reaction
A
- needs continual input of energy
3
Q
Link to exo and endo reactions (Spontaneity)
A
- most exo reactions occur spontaneously
- some endo reactions are spontaneous (ie. melting of ice)
- enthalpy change no always successful in predicting whether reaction will happen
- other factor that help to predict: change in entropy
4
Q
Entropy (S)
A
- distribution of available energy among particles
- measure of disorder of a system
- higher entropy, higher disorder
- values in J
5
Q
Signs in change in entropy
A
- +ve: entropy increases, more disorder, rxn likely to occur
- -ve: entropy decreases, less disorder
6
Q
4 factors that increase disorder in a system
A
- Increase no. of gaseous particles
- Mixing diff types of particles
- Change of state (greater dist between particles)
- Increased particle movement (temp)
7
Q
Increased no. of gaseous particles
A
e. g. N2O4 (g) –> 2NO2 (g)
- 1 mol of N2O4 gas produces 2 mol of NO2 gas
- Change in entropy = +ve (increase in disorder)
8
Q
Mixing diff types of particles (dissolution)
A
e. g. sodium chloride dissolving in water
- NaCl(s) –> Na+(aq) + Cl- (aq)
- regular arrangement of sodium ions and chloride ions replaced by random distribution of ions
- greater disorder
9
Q
Change of state
A
- solid to liquid
- liquid to gas
- molecules move more freely and quickly, greater disorder
- both endothermic but occur spontaneously due to increased entropy
10
Q
Increasing particle movement/kinetic energy
A
- heating
11
Q
Standard absolute entropy
A
- absolute entropy measured under std conditions
- 298K, 100kPa
12
Q
Zero entropy
A
- 0K, all vibrations in lattice stops
- perfect order
13
Q
Relation to Hess Law
A
- change n entropy form from one state to another
- ## always same regardless of route taken
