Chemical Reactions- Reversible reactions

Question 1

What can happen in reversible reaction?

Answer 1

The product molecules can themselves react with each other or decompose and form reactant molecules again. It can occur in both directions

Question 2

Give an example of a hydrated salt- chemical

Answer 2

CuSO4.5H20

Question 3

What are anhydrous salts?

Answer 3

Those that have lost their eater of crystallization by heating

Question 4

Give the chemical equation for the dehydration of copper (II) Sulphate

Answer 4

CuSO4.5H2O (reversible reaction sign) CuSO4 + 5H20

Question 5

What is the colour change for the dehydration of copper II sulphate

Answer 5

Blue to white

Question 6

What happens when anhydrous copper sulphate crystals are added to water?

Answer 6

They turn blue and heat is given off

Question 7

What happens when hydrous copper sulphate is heated?

Answer 7

Blue crystals turn white and a clear colourless liquid collects at the top

Question 8

Give the equation for the dehydration of cobalt(II) Chloride

Answer 8

CoCl2. 6H2O (reversible reaction sign) CoCl2 + 6H2O

Question 9

When is equilibrium reached?

Answer 9

When the rate of forward reaction = rate of reverse reaction

Question 10

What are characteristics of a reaction at equilibrium?

Answer 10

1. It is dynamic- molecules on the left and on the right of the equation are changing into each other
2. the concentration of reactant and products are constant
3. Occurs in a closed system so that none of the participating chemical species are able to leave the reaction

Question 11

In the reaction between H2 and N2 in Haber process, What is happening at the beginning?

Answer 11

When only H2 and N2 are present at the beginning of the reaction the forward reaction is at its highest since conc of H2 and N2 are at their highest

Question 12

In the reaction between H2 and N2 in Haber process, what happens after the beginning?

Answer 12

Conc of H2 and N2 decrease so the rate of forward reaction decreases and at the same time the conc of ammonia is increasing so the backward reaction increases

Question 13

In the reaction between H2 and N2 in Haber process, what happens in the end?

Answer 13

Since no gases escape, equilibrium is reached

Question 14

Give the equation for the Haber process

Answer 14

3H2 + N2 (reversible reaction sign) 2NH3

Question 15

What happens when the equilibrium position shifts to the left?

Answer 15

The concentration of reactants increase

Question 16

What happens when the equilibrium position shifts to the right?

Answer 16

The concentration of product increases

Question 17

What does the presence of a catalyst do? Why?

Answer 17

Does not affect the position of equilibrium but increases the rate at which equilibrium is reached. This is because the rate of both forward and backward reactions increase

Question 18

What is Le Chatelier’s Principle?

Answer 18

When a change is made to the conditions of a system at equilibrium the system automatically moves to oppose the change

Question 19

What happens when there is an increase in temperature?

Answer 19

Equilibrium moves in the endothermic direction to reverse the change

Question 20

What happens when there is a decrease in temperature?

Answer 20

Equilibrium moves in the exothermic direction to reverse the change

Question 21

What happens when there is an increase in pressure?

Answer 21

Equilibrium shifts in the direction that produces the smaller number of molecules of gas to decrease the pressure

Question 22

What happens when there is a decrease in pressure?

Answer 22

Equilibrium shift in the direction that produces the larger number of molecules of gas to increase the pressure

Question 23

What happens when there is an increase in concentration?

Answer 23

Equilibrium shifts to the RIGHT to reduce the effect of increase in concentration of reactant

Question 24

What happens when there is a decrease in concentration?

Answer 24

Equilibrium shifts to the LEFT to reduce the effect of decrease in reactant