the rate and extent of chemical change

Question 1

How do you calculate the mean rate of reaction?

Answer 1

mean rate of reaction = product formed OR reactant used / time

Question 2

How do you calculate the mean rate of reaction on a graph of product formed or reactant used by time?

Answer 2

the gradient

Question 3

What is collision theory?

Answer 3

Collision theory states that chemical reactions can only occur when reacting particles collide with sufficient energy. The rate is determined by the frequency of successful collisions.

Question 4

What is activation energy?

Answer 4

Activation energy is the minimum energy required for the reactants to collide with sufficient energy.

Question 5

What is the relationship between the rate of reaction and concentration?

Answer 5

As the concentration increases, the rate does as there are more particles to collide, so there is also more products.

Question 6

What is the relationship between the rate of reaction and pressure of a gas?

Answer 6

As the pressure of a gas increases, the rate does as there are more particles in one place to collide.

Question 7

What is the relationship between the rate of reaction and surface area of solids?

Answer 7

As the surface area of a solid increases, the rate does as more particles collide at once.

Question 8

What is the relationship between the rate of reaction and the temperature?

Answer 8

As the temperature increases, the rate does as the frequency of collisions and the amount of force they hit each other with increases.

Question 9

What are catalysts?

Answer 9

Catalysts increase the rate of chemical reactions but are not used up during the reaction. They allow reactions to be carried out quickly without having to raise the temperature as high, which saves money. They provide a different pathway with a lower activation energy.

Question 10

What are reversible reactions?

Answer 10

Reversible reactions are when the products can react to produce the reactants.

Question 11

How can the direction of a reversible reaction be changed? Give two examples.

Answer 11

The direction of a reversible reaction can be changed with conditions. For example,
ammonium chloride (rr arrow) ammonia + hydrogen chloride
- requires heat going forward, and cold backward

• if exothermic one way, then endothermic the other by the same amount of energy
  hydrated copper sulfate (rr arrow) anhydrous copper sulfate + water
• endo forward, exo backwards
• hydrated copper sulfate is blue, anhydrous copper sulfate is white

Question 12

What is equilibrium?

Answer 12

Equilibrium is when a reversible reaction is in a closed system and the forward and reverse reactions occur at exactly the same rate.

Question 13

What us Le Chatelier’s Principle?

Answer 13

Le Chatelier’s Principle:

if a change is made to conditions in equilibrium, then the system responds to counteract that change

Question 14

What will happen if at equilibrium, the concentration of the reactant increases?

Answer 14

If at equilibrium, the concentration of the reactant increases, more products will be formed until equilibrium is reached again.

Question 15

What will happen if at equilibrium, the temperature increases in this reaction?
2NO2 (rr arrow) N204, exo forward endo backward

Answer 15

2NO2 (rr arrow) N204, exo forward endo backward
If at equilibrium, the temperature increases, the equilibrium produces more reactant (shifts to the left) to decrease the temperature.

Question 16

What will happen if at equilibrium, the pressure increases in this reaction?
N2 + 3H2 (rr arrow) 2NH3

Answer 16

N2 + 3H2 (rr arrow) 2NH3
There are more molecules on the left as mol ratio (4:2). If the pressure increases, the equilibrium will produce more reactants so there is less molecules.

Question 17

Is bond making exothermic or endothermic?

Answer 17

Bond making is exothermic.

Question 18

Is bond breaking exothermic or endothermic?

Answer 18

Bond breaking is endothermic.