C8- Rates And Equilibrium

Question 1

How can you find out the rate of a chemical reaction?

Answer 1

1) You can find out the rate of a chemical reaction by monitoring the amount of reactants used up over time.
2) You can also find out the rate of reaction by measuring the amount of products made over time.

Question 2

What is the minimum amount of energy that particles must have in order to react called?

Answer 2

1) Activation Energy.

Question 3

How might the rate of a chemical reaction increase?

Answer 3

1) The rate of a chemical reaction increases if the Surface Area : Volume ratio of any solid reactants is increased.

Question 4

How does temperature effect the rate of reaction?

Answer 4

1) As the temperature of a reaction increases, the reaction will happen more quickly.

Question 5

Why does increasing the temperature of a reaction increase the rate of reaction?

Answer 5

1) Particles collide more frequently and with more energy. If more collisions take place, a higher proportion of particles have energy greater than the activation energy.

Question 6

What happens if you increase the concentration of reactants in solutions between particles? Explain why.

Answer 6

1) The frequency of collisions will increase and therefore the rate of reaction will increase. If the concentration is higher, there are more reacting particles which means that they can collide more frequently and therefore the rate of reaction increases.

Question 7

What will happen when you increase the pressure of reacting gases?

Answer 7

1) Increasing the pressure also increases the frequency of collisions and so does the rate of reaction.

Question 8

What does a catalyst do? What happens to it during a reaction?

Answer 8

1) A catalyst speeds up the rate of a chemical reaction.

2) It is not used up itself during the reaction, it remains chemically unchanged.

Question 9

How do Catalysts increase the rate of reaction?

Answer 9

1) Increases the rate of reaction by providing a different pathway for the reaction that has a lower activation energy.

Question 10

When might catalysts be used?

Answer 10

1) Catalysts are used whenever possible in industry to increase rates of reaction and reduce energy costs.

Question 11

How might catalysts be used in the industry?

How might they help save the environment?

Answer 11

1) Catalysts are often very expensive/precious metals such as Gold, Platinum.
2) Catalysts help save money and the environment. Using high temperatures and pressures involves burning fossil fuels. When you use a catalyst, temperatures and pressures are lower, which conserves these non-renewable sources.

Question 12

What happens to Catalysts in chemical plants?

Answer 12

1) In chemical plants, the catalysts become poisoned so that they don’t work anymore.
2) This happens because impurities in the reaction mixture combine with the catalyst and stop it from working properly.

Question 13

What does the Collision Theory state?

Answer 13

1) The collision theory states that chemical reactions can occur only whern the reacting particleds collide with eachother and with sufficient energy.

Question 14

What are reversible reactions?

Answer 14

1) Reversible reactions are reactions where the products of the reaction can react to produce the original reactants.
2) A+B=C+D. Eg: ammonium chloride = ammonia
= hydrogen chloride

Question 15

Explain what happens if a reaction is endothermic or exothermic in regards to reversible reactions

Answer 15

1) The same amount of energy is transferred.

Question 16

What does equilibrium mean?

Answer 16

1) When a reversible reaction occurs in apparatus which prevents the escape of reactants and products, equilibrium is reached when the forward reactions occur at the exact same rate.

Question 17

What are the effects of changing conditions on a system in equilibrium?

Answer 17

1) If a system is at equilibrium and a change is made to any of the conditions then the system responds to counteract the change.
2) The effects of changing conditions on a system at equlibrium can be predicted using Le Chatelier’s Principle.

Question 18

What is effecrt of changing concentration in a system?

Answer 18

1) If concentration is changed, then the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again.
2) If the concentration of a reaction is increased, more products will be formed until equilibrium is reached again.
3) If the concentration of a product us decreased, more reactants will react until equilibrium is reached again.

Question 19

What are the effects of temerature changes on equilibrium?

Answer 19

1) If the temp of a system at equilibrium is increased:
The relative amount of products at equilibrium increases for an endothermic reaction. The relative amount of products at equilibrium decreases for an exothermic reaction.
2) If the temp of a system at equilibrium is decreased:
The relative amount of products at equilibrium decreases for an endothermic reaction.
The relatiive amount of products at equilibrium increases for an exothermic reaction.

Question 20

What are the effects of pressure changes on a system at equilibrium?

Answer 20

1) An increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules as shown by the symbol equation for that reaction.
2) A decrease in pressure causes the equilibrium position to sift towards the side with the larger number of molecules as shown by the symbol equation for that reaction.

Question 21

What does Le Chatelier’s principle state?

Answer 21

1) Whenever a change in condition is introduced to a system at equilibrium, the position shifts so as to cancel out the change.