Chemical Equilibrium

Question 1

Rate of reaction speed

Answer 1

Tends to decrease with time. This happens because there are less atoms left to react as time increases

-(think of bumper cars : less cars left, longer it takes for the reaction to occur)

Question 2

What is chemical equilibrium?

Answer 2

A state at which the rates of forward and reverse reactions are equal
AND
the concentrations of the reactants and products ramain constant (don’t have to be equal)

Question 3

What changes can we observe at equilibrium?

Answer 3

There are no observable change
BUT
it is dynamic, meaning both forwards and backwards reactions take place but their rates are equal so there are no measurable change in concentration of reactants or products.

Question 4

What conditions must be met to establish equilibirium?

Answer 4

1. Reversible reaction
2. Closed system
3. Temperature must remain the same

Question 5

What is Keq

Answer 5

A mathematical ratio which represents the proportion of products to reactants.

Question 6

What does it mean id Keq > 1

Answer 6

The forwards reaction is favoured
- reaction “goes to completion” and all or most of the reactants are used up to form products

Question 7

What does it mean if Keq < 1

Answer 7

The reverse reaction or reactants is favoured
- most of the reactants remain unchanged and there are few products produced

Question 8

What does “favoured” mean in terms of reaction

Answer 8

It means that side of the equation has the higher number of moles and higher concentration than the other

Question 9

What does ice chart stand for?

Answer 9

I : Initial concentrations
C : Change in the concentrations as the system moves towards equilibrium
E : equilibrium concentrations

Question 10

What does Le Chatelier’s Principle represent?

Answer 10

It states that if a system at equilibrium is subjected to an external stress, the equilibrium will shift to minimize the effects of that stress.

Question 11

CP - changes in concentration

Answer 11

A + 2B <–> C + D
INCREASE in concentration A causes shift to RIGHT
DECREASE in concentration causes sift to the LEFT

Question 12

CP - change in Volume & Pressure

Answer 12

A + 2B <–> C + D
only affected if gas is present

• if you INCREASE the pressure equilibrium moves to side with fewest moles
• if you DECREASE the equilibrium moves to the side with most moles of gas

**Pressure is typically increased by reducing volume

Question 13

CP - change in temperature

Answer 13

INCREASING favours the ENDOthermic reaction
- move to left
- more products are made

DECREASING favours the EXOthermic reaction
- move to right
- more reactants are made

alters the value of Keq since one entire side is favoured over the other

Question 14

CP - adding a catalyst

Answer 14

No changes since both forwards and reverse reactions speed up. Helps reaction reach the point of equilibrium sooner.