6.2 Changing conditions of equilibrium reaction

Question 1

What happens to equilibrium is proportion of products in equilibrium mixture is increased

Answer 1

Equilibrium is moved to the right or in the forward direction

Question 2

What happens to equilibrium is proportion of products in equilibrium mixture is decreased

Answer 2

Equilibrium is moved to the left, or in backwards direction

Question 3

What is Le Chateliers principal

Answer 3

If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance

So equilibrium shifts to oppose the change

Question 4

Why can you not predict the quantities involved with le chateliers principal

Answer 4

The principal doesn’t tell us how far the equilibrium moves, it just tells us what direction it moves

Question 5

What would happen to equilibrium if you increased concentration of reactants eg reactant A

A + B <–> C + D

Answer 5

Eg A + B <–> C + D
- The equilibrium shifts in the direction that will reduce the concentration of reactant A
- The system can reduce concentration of A by reacting it with B (which will form more C and D)
So adding more A uses up more B which will increase amount of product

So this moves equilibrium to the right as more products are made

Question 6

How does changing pressure affect equilibrium
(It only affects reactions with gases)

Answer 6

. Changing pressure will only change position of equilibrium if there are different numbers of molecules on each side
. Increasing pressure means there are more molecules of the gas in the same volume

So increasing pressure, the equilibrium will move to decrease this
So it moves to the side with fewer molecules because fewer molecules exert less pressure

If you decrease pressure, the equilibrium shifts to side with more molecules to exert more pressure

Question 7

In reaction
N2O4 <–> 2NO2
What would happen to equilibrium is pressure was increased

Answer 7

There are more molecules on the right than are on the left
Equilibrium wants to reduce this pressure so shifts to the left as there are fewer molecules

This means a colourless solution forms (N2O4) and it changes from brownish (2NO2)

Question 8

How do endothermic / exothermic change depending on the direction of the reaction

Answer 8

Reversible reactions that are exothermic in one direction are endothermic in the other

Question 9

How does increasing temperature affect the equilibrium in reactions

Answer 9

When the ΔH is negative, you know that the forward reaction is exothermic

When temperature is increased, the equilibrium will shift in the direction that cools the system down, so it will move to the left side, the endothermic side.
This side absorbs heat, cooling the system down

Question 10

How does decreasing the temperature affect equilibrium in reactions

Answer 10

If the forward reaction is exothermic, decreasing temperature means the system wants to get warmer

So the equilibrium will shift to the exothermic direction to release heat, warming the system up

Question 11

What do catalysts do in equilibrium reactions

Do they affect equilibrium

Answer 11

Catalysts don’t effect position of equilibrium, they work by providing an alternative route for the reaction which has a lower activation energy

Catalysts have no affect on yields of reactions (how much product is made)
But they allow equilibrium to be reached more quickly which is why they are used in industry