Chapter 2

Question 1

Characteristics of chemical equilibrium

Answer 1

1) rates of forward and reverse are equal
2) macroscopic properties (measurable) are constant (temp, [])
3) these reactions can start from either the reactants or the products
4) A system not at equilibrium will tend to move to equilibrium ( reaction is dynamic)

Question 2

Enthalpy

Answer 2

Heat energy of a system

Tend towards min enthalpy

• tend towards exothermic

Question 3

Entropy

Answer 3

Randomness or chaos of a system

-tend towards max entropy
S increasing entropy

Question 4

Three types of reactions

Answer 4

1)enthalpy and entropy tend towards products
-reaction will start and go to completion
2)enthalpy and entropy tend towards reactants
-reaction will not start
3)enthalpy and entropy: one tends to one side, one tends to other
-reaction will start and go into equilibrium
-

Question 5

Le chateliers principal

Answer 5

A system in equilibrium will react to a stress in such a way as to counteract that stress and form a new equilibrium state

Question 6

Change in temp

Answer 6

Equilibrium will shift towards endothermic

If temp decreased it shift towards exothermic

Question 7

Change in concentration

Answer 7

• Increase [r] = shift to products
• increase [p] = shift to reactants
• decrease [r] = shift to reactants
• decrease [p] = shift to products

Question 8

Change in pressure

Answer 8

Only affect equilibriums if the change in p is due to volume change

Question 9

Change in volume

Answer 9

Increase V = shift to side with largest # of gas particles

Decrease V = shift to side with fewest # of gas particles

Question 10

Keq the constant of equilibrium

Answer 10

Describes the position of the equilibrium
Only a change in temp will change the value of the constant

• for gasses, aq, and 2 or more liquids
• products over reactants

Question 11

Keq ratios

Answer 11

Keq < 1 : reactants are favoured (higher [])
Keq = 1 : ratio of R to P is equal
Keq > 1 : products are favoured

Question 12

I. C. E

Answer 12

I = [initial]
C = [change in]
E = [equilibrium]

Question 13

Why does temp change in equilibrium

Answer 13

When the amount of heat is decreased, the reaction “shifts” so as to produce more heat

Question 14

Why does [] change in equilibrium

Answer 14

When the [] increases, the reaction shifts so as to partly decrease the amount of added

Question 15

Why does pressure change in equilibrium

Answer 15

If the pressure is increased the reaction will shift to the side having the least number of gaseous molecules

Question 16

Catalyst

Answer 16

Adding a catalyst speeds up the forward and reverse rates by an equal amount, so that a reaction at equilibrium remains at equilibrium

Question 17

Trial keq. Keq

Answer 17

If trial keq doesn’t = keq it’s not a equilibrium

• trial keq < keq = shift to products
• trial keq = keq = no shift
• trial keq > keq = shift to reactants