C8.1-9 - Rates and Equillibrium

Question 1

How do you calculate the Rate of a Reaction?

Answer 1

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

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

Rate of Reaction - cm^3/s or g/s

Question 2

How do you calculate the gradient of a curve?

Answer 2

Draw tangents to the curves on these graphs and use the slope of the tangent as a measure of the rate of reaction.

Question 3

What is collision theory?

Answer 3

Collision theory explains how various factors affect rates of reactions. According to this theory, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.

Question 4

What is Activation energy?

Answer 4

The minimum amount of energy that particles must have to react is called the activation energy.

Question 5

What factors increase the rate of reaction?

Answer 5

• temerature
• surface area of solids
• concentration of solution or pressure of gases
• the presence of a catalyst

Question 6

What is a catalysts?

Answer 6

Chemical substance that speeds up reaction without being used up, it remains chemicallly unchanged.

Question 7

What is a reversible reactions and how are they written?

Answer 7

In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented:

A+B ⇌ C+D

Question 8

What is an examples of reversible reactions?

Answer 8

Heat
Ammonium Chloride ⇌ ammonia + hydrogen chlorode
Cool

Question 9

What is Dynamic Equilibrium?

Answer 9

At equillibrium, the rate of the forward reaction equals the rate of the reverse reaction.

Question 10

What is the ‘Le Chatelier’s’ principle?

Answer 10

If a change is made to the conditions of a system at equallibrium, then the position of equilibrium moves to cancel out the change in conditions. This principle can be used to predict how the position of equilibrium will change when the reaction conditions are changed.

Question 11

Describe and explain the effect of changing the conditions on Equilibrium?

Answer 11

If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.

Question 12

Describe and explain the effect of changing the conditions on Concentration?

Answer 12

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

If the concentration of a product is decreased, more reactants will react until equilibrium is reached again.

Question 13

Describe and explain the effect of changing the conditions on Tempreture is Decreased?

Answer 13

• The relative amount of products at equilibrium decreases for an endothermic reaction
• The relative amount of products at equilibrium increases for an exothermic reaction.

Question 14

Describe and explain the effect of changing the conditions on Pressure?

Answer 14

• 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
• A decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction.

Question 15

Why are Catalyst used in the Industry?

Answer 15

Catalysts are used whenever possible in industry to imcrease rates of reactiom and reduce energy costs, maximise profit.

Question 16

What is the rule for a exothermic and endothermic reactions in reversable reaction?

Answer 16

If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction. The same amount of energy is transferred in each case

Question 17

Describe and explain the effect of changing the conditions on Tempreture is Increased?

Answer 17

• The relative amount of products at equilibrium increases for an endothermic reaction
• The relative amount of products at equilibrium decreases for an exothermic reaction.