Ch8 Rates and Equilibrium

Question 1

mean rate of reaction

Answer 1

quantity of reactant used/ time taken

quantity of product formed/ time taken

Question 2

5 Factors affecting rate of chemical reaction

Answer 2

pressure of reacting gases
SA of solid reactants
temperature
presence of catalysts
concentration of reactants in solution

Question 3

collision theory

Answer 3

For a reaction to take place, particles have to collide with enough energy to cause it(proportional)

Question 4

Activation energy

Answer 4

minimum amount of energy particles must have before they can react

Question 5

increasing chance of particles reacting

Answer 5

increasing frequency of reacting particles colliding

Increasing the energy particles have when they collide

Increasing amount of energy is more effective than increasing frequency of collisions

Question 6

the effect of temperature

Answer 6

After heating particles, energy is transferred to the particles. This makes particles move faster which increases the frequency of collisions

Particles have more energy than the activation energy, meaning more successful collisions take place

Question 7

the effect of concentration

Answer 7

increased concentration means they are more particles moving around in the same volume of solution
this increases the frequency of collisions

Question 8

the effect of pressure

Answer 8

an increase in pressure squashes the gas particles closer together
more particles of gas in a given volume
increases the frequency of collisions

Question 9

catalyst

Answer 9

substance that increases the rate of reaction
doesn’t chemically change the reaction(can be re-used) and isn’t used up
different reaction need different catalysts

Question 10

effect of catalysts

Answer 10

provides a different pathway for the reaction that has a lower activation energy
frequency of effective collisions increase

Question 11

effect of SA of reactants

Answer 11

the larger the SA:V ratio, the more particles are exposed to the other reactant
There is a greater chance of particles colliding, which increases rate of reaction

Question 12

reversible reaction representation

Answer 12

A + B ⇌ C + D

Question 13

reversible reaction

Answer 13

products can react together to re- make the original reactants

Question 14

example of reversible reaction

Answer 14

ammonia chloride ⇌ ammonia + hydrogen chloride

Question 15

energy changes in a reversible reaction

Answer 15

Same amount of energy is transferred in both directions(energy cannot be created or destroyed in a chemical reaction)

If the reactions is endothermic in one direction, it is exothermic in the other

Question 16

Example of energy change in a reversible reaction

Answer 16

hydrated copper sulphate ⇌ anhydrous copper sulphate + water

endothermic forwards
exothermic backwards

Question 17

Dynamic equilibrium

Answer 17

The rate of forwards reactions equals the rate of the reverse reactions

Question 18

Le Chatelier’s principle

Answer 18

If a system is at equilibrium and a change is made to any of the conditions, the position of equilibrium shifts to cancel out the change(re-establish equilibrium)

Question 19

Importance of Le Chatelier’s principle

Answer 19

industrial chemists need to find the conditions that give as much product as possible in as short a time as possible

Question 20

If forward reaction is endothermic, what happens if the temperature of a system at equilibrium is increased

Answer 20

the amount of products formed is increased

Question 21

If forward reaction is exothermic, what happens if the temperature of a system at equilibrium is increased

Answer 21

the amount of products formed is decreased

Question 22

If the forward reaction produces more molecules of gas, an increase in pressure does what

Answer 22

decreases the amount of products formed

Question 23

If the forward reaction produces less molecules of gas, an increase in pressure does what

Answer 23

increases the amount of products formed