Equilibrium

Question 1

Dynamic equilibrium

Answer 1

Rate of the forward reaction= rate of the backward reaction, no change in position

E.g. a treadmill

Question 2

Static equilibrium

Answer 2

Stationary, no movement

E.g. a ruler balanced at its centre

Question 3

Reversible reaction

Answer 3

The reaction is going in both directions, the product reacts to gave back the reactants

Question 4

Chemical equilibrium

Answer 4

A state of dynamic balance in a reversible reaction, where the rate of the forward reaction= rate of the backward reaction

Question 5

Dynamic state

Answer 5

The reactants are continuously forming products and the products are continuously forming reactants

Question 6

Le Chatelier’s Principle

Answer 6

If a stress is applied to a system at equilibrium, the system readjust to relieve the stress (to become balanced again)

Question 7

E.g. of an unreversible reaction

Answer 7

2Mg+O2–>2MgO (magnesium oxide)

Question 8

What did Haber discover?

Answer 8

Nitrogen+Hydrogen—>Ammonia (used in fertilisers)

The reaction didn’t go completely from left to right, this is how he discovered reversible reactions

Question 9

What happens if the rate of the forward reaction decreases?

Answer 9

Rate of the backward reaction increases until they become qual again (dynamic state)

Question 10

What type of “stress” can be applied to a system?

Answer 10

Change in conditions of reaction,
Conc. of reactant/ product
Temp

Question 11

Exothermic reaction

Answer 11

Forward rxn, gives out heat

Question 12

Endothermic

Answer 12

Backward rxn, takes in heat

Question 13

Summarise La Chatelier’s findings

Answer 13

Le Chatelier’s Principle predicts that in an all-gaseous reaction, an increase in pressure will favour the reaction that brings about a reduction in volume (will shift towards side with less molecules)

Question 14

What type of equilibrium reaction will a change in pressure effect?

Answer 14

An equilibrium rxn with an uneven number of molecules of gaseous reactants & products

Question 15

What will a change in pressure do to a reaction with an even no. of gaseous molecules on each side?

Answer 15

Pressure change has no effect on equilibrium

Question 16

What effect does a catalyst have on a dynamic equilibrium?

Answer 16

The catalyst speeds up the rate at which the equilibrium is reached, but no change in position of the equilibrium

Question 17

Increase in conc. of the reactant?

Answer 17

The equilibrium shifts to the right

Question 18

Increase in temperature?

Answer 18

equilibrium shifts in a backwards direction (endothermic rxn) to absorb the heat

Question 19

Industrial uses of Le Chatelier’s Principle?

Answer 19

Production of NH3 by Hager Process (fertilisers/ cleaning agents)

Production of Sulfuric acid by Haber Process

Question 20

What does the amount of NH3 produced depend on?

Answer 20

Temp. & pres. inside reaction vessel

Question 21

What will produce a good yield of NH3?

Answer 21

High pressure—> pushed to right (products)

Low temp

Question 22

Disadvantage of a high pressure plant?

Answer 22

Expensive & dangerous (gas leaks/explosions)

Question 23

Benefit of a catalyst in industry?

Answer 23

Speeds up reaction to produce products fast

Allows reaction to be carried out at a lower temp

Question 24

Why is it hard to keep the temp. low in industry, even though its desired to be low?

Answer 24

Low temp.—> reaction too slow to be economically viable

Question 25

What is the one factor that affects Kc?

Answer 25

Temperature

Question 26

Larger the Kc?

Answer 26

More products, equil. Shifts to the right

Question 27

Small Kc value indicates?

Answer 27

Only a small amount of the reactants have been converted to products

Question 28

What does the Kc tell us?

Answer 28

How far the reaction has gone, not the Rate of Reaction

Question 29

What changes would the increase in pressure have on the Kc value?

Answer 29

No change