Unit 9 - Entropy and Free Energy

Question 1

Spontaneity

Answer 1

a reaction will occur spontaneously if it does not require the input of any additional energy;
may occur rapidly or over many years

Question 2

Entropy

Answer 2

related to disorder;
increases as the number of atoms increase, mass of the atoms increase, temperature increases, during phase changes; expansion or mixing of gases; formation of solutions

Question 3

Second law of thermodynamics

Answer 3

all spontaneous processes increase the entropy of the universe;
therefore the change in entropy of the system + change in entropy of the surroundings in always greater than 0

Question 4

Third law of thermodynamics

Answer 4

the entropy of a pure, perfect crystal at 0 K has 0 entropy

Question 5

Free energy and phase transitions

Answer 5

for a phase transition, the change in free energy is always zero

Question 6

Airbags

Answer 6

sodium azide decomposes into sodium (metal) and nitrogen gas;
increases in entropy;
then, the sodium reacts with potassium nitrate, forming metal oxides and nitrogen gas;
finally, metal oxides react with silicon dioxide to form alkaline glass