Reactivity 1.4 (HL)

Question 1

Entropy (S)

Answer 1

Measure of the ways in which the available energy of a system can be distributed among the particles of a system (JK-1 mol-1)

Question 2

Can entropy be measured?

Answer 2

Yes, absolute values can be measured

Question 3

Why would entropy increase (4 ways)

Answer 3

• Mixing different states
• Increasing distance between particles (changing state)
• Increasing movement of particles (increasing temperature)
• Increasing the number of particles (mol ratio)

Question 4

Entropy change formula

Answer 4

Differences between the total entropy of the products and the total entropy of the reactants (Sp - Sr)

Question 5

Gibbs Energy Change (g)

Answer 5

Energy obtained from a chemical reaction that is available to do work (kj mol-1)

Question 6

Value of G

Answer 6

Always negative as it is energy obtained

Question 7

Gibbs energy change formula

Answer 7

G = H - T S

Question 8

Spontaneous reaction

Answer 8

System becomes more stable (able to do work) Once started, it does not need any additional energy. G must be negative

Question 9

Reaction Quotient (Q)

Answer 9

Ratio of products and reactants concentration when not at equilibrium

Question 10

Equilibrium constant (K)

Answer 10

Value of the reaction quotient in equlibrium.

Question 11

When is K=0?

Answer 11

G is greater than 30kj mol-1
No reaction - impossible.

Question 12

When is K smaller than 1?

Answer 12

G is between 0 and 30 kjmol1
Partial reaction occurs

Question 13

When is K=1?

Answer 13

When G=0
Partial reaction occurs

Question 14

When is K greater than 1?

Answer 14

G is greater than 0 and 30kjmol
Partial reaction occurs

Question 15

When is K»1?

Answer 15

G is smaller than -30kjmol
Complete reaction occurs