Kinetics and Equilibrium

Question 1

how can the rate of reaction be calculated?

Answer 1

amount of reactant used or amount of product formed/time

Question 2

what affect does a change in surface area of a solid have on the rate of reaction?

Answer 2

if there is more surface area that is in contact, it’s more likely there will be successful collisions that lead to a reaction=faster rate of reaction

Question 3

what affect does the concentration of solution have on the rate of reaction?

Answer 3

there’s more particles so it’s more likely that there will be successful and more frequent collisions that lead to a reaction=faster reaction

Question 4

what affect does pressure have on the rate of reaction?

Answer 4

the particles are closer together causing more collisions that lead to a reaction=faster reaction

Question 5

what affect does temperature have on the rate of reaction?

Answer 5

particles gain more energy and move faster if there is a higher temperature, so they collide more frequently

Question 6

what affect does the use of a catalyst have on the rate of reaction?

Answer 6

a catalyst increases the rate of reaction without being used up. They do this by lowering the activation energy/ With a catalyst, more collisions result in a reaction, so the rate of reaction increases

Question 7

what is activation energy?

Answer 7

the energy needed to get the reaction started

Question 8

how does a catalyst speed up the rate of reaction?

Answer 8

it provides and alternate pathway with lower activation energy without being used up. They do this by lowering the activation energy needed. With a catalyst, more collisions result in a reaction, so the rate of reaction increases

Question 9

what is a catalyst?

Answer 9

a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Question 10

what symbol is used when reactions are reversible?

Answer 10

⇌

Question 11

why are some reactions reversible?

Answer 11

some reactions can happen both ways: the reactants can make the products and the products can make the reactants

Question 12

describe the reversible reaction of hydrated copper sulphate

Answer 12

• if you add water to it, it will become blue hydrated copper sulfate
• if you heat it up (remove the water), it will become white anhydrous copper sulfate powder

Question 13

describe the effect of heat on ammonium chloride

Answer 13

• if heated, ammonium chloride splits up to form ammonia and hydrogen chloride
• if ammonia and hydrogen chloride reacts with each other, it forms ammonium chloride

Question 14

what are dynamic reactions?

Answer 14

when forward and reverse reactions occur at the same time, and never stop

Question 15

what is an equilibrium?

Answer 15

when the rate of the forward reaction is equal to the rate of the reverse reaction, the reaction is said to have reached equilibrium

Question 16

how is an equilibrium reached?

Answer 16

if reversible reactions happen in a closed system (meaning none of the reactants or products can escape), equilibrium will always be reached

Question 17

what is the effect of a catalyst on an equilibrium?

Answer 17

a catalyst doesn’t alter the position of equilibrium, it only makes the reaction reach equilibrium faster

Question 18

what happens if you remove a product from an equilibrium?

Answer 18

the equilibrium mixture changes to make more products, to try and balance out the reaction, just like it was previously. The same thing happens if you try and remove a reactant: equilibrium changes to produce more of the reactant

Question 19

what are the effects of changing the pressure on the equilibrium position in reversible reactions?

Answer 19

• if the pressure increases, equilibrium moves to the side with the least molecules
• if pressure decreases, equilibrium moves to the side with the most molecules

Question 20

what are the effects of changing temperature on the equilibrium position in reversible reactions?

Answer 20

• if the temperature increases, the endothermic reaction will increase, to absorb the extra heat
• if the temperature decreases, the exothermic reaction will decrease, to give out more heat

Question 21

what happens to the amount of product in an equilibrium mixture when the temperature is changed?

Answer 21

• if the forward reaction is exothermic and the temperature is increased, the yield of products is decreased. If the temperature is decreased, the yield of products is increased
• if the forward reaction is endothermic and the temperature is increased, the yield of products is increased. If the temperature is decreased, the yield of products is decreased

Question 22

describe an experiment to investigate the effects of changes in surface area of a solid on rate of reaction

Answer 22

1. put magnesium (of a known mass) in hydrochloric acid
2. time the reaction
3. change the form of magnesium to powder, strips or wires, whilst keeping the same mass
4. the more surface area (the smaller the pieces of magnesium) the faster the rate of reaction

Question 23

describe an experiment to investigate the effects of concentration of solutions on the rate of reaction

Answer 23

1. put marble chips (of a known mass) into dilute hydrochloric acid
2. time the reaction
3. increase the concentration of hydrochloric acid (change the ratio of water to hydrochloric acid)
4. the more concentrated the hydrochloric acid (the lower the ratio of water) the faster the reaction

Question 24

describe an experiment to investigate the effects of temperature on the rate of reaction

Answer 24

1. put magnesium powder (of a known mass) into a known mass of hydrochloric acid
2. time the reactions
3. repeat the experiment at different temperatures
4. the higher the temperature the faster the rate of reaction

Question 25

describe an experiment to investigate the use of a catalyst on the rate of reaction

Answer 25

1. put magnesium dioxide into hydrogen peroxide
2. this will decompose into water and oxygen, without the manganese dioxide being used up
3. add more of the catalyst, to see if the reaction quickens
4. the more of the catalyst, the faster the reaction