C8 - Rates of reaction

Question 1

What is the equation for rate of reaction(reactant)?

Answer 1

mean rate of eaction = quantity of reactant used/time taken

Question 2

What is the equation for rate of reaction(product)?

Answer 2

mean rate of reaction = quantity of product formed/time taken

Question 3

The quicker the rate of reaction..

Answer 3

The higher in the reactivity series

Question 4

Rate of collisions

Answer 4

Depends on how often particles collide
and the amount of energy transferred during a collision

Question 5

What are the factors affecting the rates of chemical reactions?

Answer 5

• Concentrations of reactants or pressure of reacting gases
• Surface area of solid reactants
• Temperature
• Catalyst present

Question 6

How does concentration or pressure affect the rate?

Answer 6

The more particles in an area the more frequent the collisions

Question 7

How does surface area of solid reactants affect the rate?

Answer 7

The smaller the pieces, the more area for collisions to happen on

Question 8

How does temperature affect the rate?

Answer 8

The more the temperature, the more kinetic energy particles have, colliding more frequently

Question 9

How do catalysts affect the rate?

Answer 9

Catalysts speed up the reaction

Question 10

RP5 - Method when at least one of the products is a gas

Answer 10

1. Equipment: conical flask, delivery tube, gas syringe
2. Add 10g of _ into the flask
3. Add 50cm3 of ____. connect the gas syringe and start a timer
4. Dependent variable: total volume of gas made in 1 minute

Question 11

RP5 - Method when at least one of the products is a gas 2

Answer 11

1. Equipment: balance, conical flask, cotton wool
2. Add 10g of ____. into the flask
3. Add 50cm3 of ____. and start a timer
4. Dependent variable: Total mass lost in 1 minute

Question 12

RP5 - Method when one of the products is a solid

Answer 12

1. Equipment: black cross drawn on paper, conical flask
2. Put 50cm3 of sodium thiosulfate solution into a conical flask
3. Put conical flask on a cross drawn on a piece of paper
4. Add 5cm3 of dilute hydrochloric acid and start timer
5. Dependent variable: Time it takes for cross to disappear
6. Control: concentration, volume

Question 13

RP5 - What is turbidity?

Answer 13

The cloudiness of a solution due to the presence of particles invisible to the eye suspended in the fluid

Question 14

RP5 - How can you tell from a symbol equation if the solution is going to turn clody?

Answer 14

When one of the products is a solid (s) symbol after it

Question 15

RP5 - How can you calculate the rate of reaction at a specific time?

Answer 15

Draw a tangent to the curve and calculate using difference in y-axis/difference in x-axis

Question 16

RP5 - When investigating the rate at which a precipitate forms why should the same person look at the black cross?

Answer 16

Different people may decide they cannot see the cross at different amounts of cloduiness, lead to errors regarding reaction time

Question 17

RP5 - What does reproducible/repeatable mean?

Answer 17

If the experiment is repeate dby antoher pesron, the same results are obtained

Question 18

What is collision theory?

Answer 18

A theory that states that chemical reactions can only occur when reacting particles collide with each other and with sufficient energy

Question 19

What is activation energy?

Answer 19

The minimum amount of enegry that particles must have to react

Question 20

Why does increasing pressure/surface area increase the rate of reaction?

Answer 20

The frequency of collisions between reactants is increased which increases rate

Question 21

Why does increasing temperature increase the rate of reaction?

Answer 21

The frequency of collisions between reactants is increased and the collisions are more energetic

Question 22

Why do catalysts increase the rate of reaction?

Answer 22

They provide a different pathway for the reaction that has a lower activation energy

Question 23

What is the symbol for reversible reactions?

Answer 23

⇌

Question 24

What is a reversible reaction?

Answer 24

A reaction in which the products can react to make the original reactants

Question 25

How can the direction of a reversible reaction be changed?

Answer 25

Changing the conditions

Question 26

Explain energy changes and reversible reactions?

Answer 26

- If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction - Same amount of energy is transferred

Question 27

What is equilibrium?

Answer 27

- When a reversible reaction occurs in apparatus which prevents the escape of reactants and products - Equilibrium is reached when the forward and reverse reactions occur at the same rate

Question 28

What is Le Chatelier's principle?

Answer 28

- If stress is applied to a system in equilibrium, the system shifts in the direction that relieves the stress

Question 29

What happens if the concentration of a reactant is increased?

Answer 29

More products will be formed until equilibrium is reached again

Question 30

What happens if the concetration of a reactant is decreased?

Answer 30

More reactants will react until equilibrium is reached again

Question 31

What happens if the temperature of a system is increased in an ENDOTHERMIC reaction?

Answer 31

Amount of products increases

Question 32

What happens if the temperature of a system is increased in an EXOTHERMIC reaction?

Answer 32

Amount of products decreases

Question 33

What happens if the temperature of a system is decreased in an ENDOTHERMIC reaction?

Answer 33

Amount of products decreases

Question 34

What happens if the temperature of a system is decreased in a EXOTHERMIC reaction?

Answer 34

Amount of products increases

Question 35

What happens if there is an increase in pressure?

Answer 35

Equilibrium will shift to side with smaller number of molecules

Question 36

What happens if there is a decrease in pressure?

Answer 36

Equilibrium shifts to the side with larger number of molecules