Energetics(2)

Question 1

What is entropy

Answer 1

• entropy measures the degree of disorder in matter
• the greater the number of ways to distribute particles and their energies within the system
• the greater the degree of disorder in the system
• larger the entropy of system

Question 2

How does temperature affect entropy of chemical system

Answer 2

• when temperature increases, the average kinetic energy of particles increases
• particles move more randomly and vigorously
• kinetic energies will be distributed over a wider range at a higher temperature
• more ways to distribute the particles and their energies in the system
• greater disorder in the system
• entropy of system increases when temperature increases

Question 3

How does change in phase affect entropy (solid to liquid)

Answer 3

• order in solid is destroyed
• particles in liquid can now move about more freely and there are more ways to distribute the particles and their energies
• greater disorder in the system
• increase in entropy

Question 4

How does change in phase affect entropy ( liquid to gas )

Answer 4

• gas particles can now move with great disorder in a larger volume of space as compared to particles in liquid
• there are even more ways to distribute the particles and their energies
• greatest disorder in the system among the three states
• even greater increase in entropy

Question 5

How does change in number of gaseous particles affect entropy

Answer 5

• when the products of a reactant contain more gas particles than the reactants
• there are more ways to distribute the particles and their energies
• the greater disorder in the system results in an increase in entropy of the system

Question 6

How does mixing of gases affect entropy

Answer 6

• when mixing gases, each gas expands to occupy the whole container
• there are more ways to distribute the particles and their energies in the system
• resulting in a greater disorder in the system
• entropy increases

Question 7

How does mixing of liquids affect entropy

Answer 7

• when mixing liquids of similar polarities
• the molecules have greater volume of space to move about
• there are more ways to distribute the particles and their energies in the system
• resulting in a greater disorder in the system
• entropy increases

Question 8

How does dissolving an ionic solid affect entropy

Answer 8

• entropy increases as the giant ionic lattice breaks down and the ions are free to move
• entropy decreases because water molecules form ion-dipole attraction. With the ions, resulting in the water molecules becoming more restricted in their movement

Question 9

What is Gibbs free energy of a reaction

Answer 9

• measure of the spontaneity of the reaction and the useful energy available from it

Question 10

What does Gibbs free energy tell about spontaneity of reaction

Answer 10

• G>0 — reaction is not spontaneous
• G<0 — reaction is spontaneous
• G=0 — reaction is at equilibrium