Topic 9: Reversible Reactions

Question 1

What is a reversible reaction?

Answer 1

A chemical change that is able to go backwards and forwards.

Question 2

To represent a chemical process we use….?

Answer 2

Half arrows (=)

Question 3

Experiment 1: Reversible reaction of acids and bases (3rd form)?

Answer 3

Change color of Phenolpholein by adding a few drops of NaOH (aq) to change the solution -> pink, then changing it back by adding HCL (aq) -> colorless

Question 4

Experiment 2: Reversible reaction, testing for water?

Answer 4

CuSO4. 5H2O(s) ->(heat) (H2O)<- CuSO4(s) 5H2O

Question 5

Experiment 3: Reversible reaction, of states of matter 3rd form - diffusion?

Answer 5

NH4Cl(s)(white solid) ->(heat) (cool)<- NH3(g) + HCL(g) (colorless)

Question 6

What is Chemical Equilibrium?

Answer 6

This is “When the rate of forward reaction equals the rate of the backwards reaction”, the reaction is said to be in equilibrium.

Question 7

What is a dynamic Equilibrium?

Answer 7

The type of equilibrium that occurs in chemical reactions is called a dynamic equilibrium.

Question 8

How is the position of a Equilibrium changed?

Answer 8

The position of a equilibrium can be changed by altering the concentrations of reactants or products, temperature or pressure.

Question 9

How can the concentration change the position of the equilibrium?

Answer 9

A + B == C + D

- If more A is added the equilibrium moves to the right to reduce the concentration of A.

Question 10

How can the temperature change the position of the equilibrium?

Answer 10

A + B == C + D = Heat
- When the forward reaction is exothermic, if the temperature is increased, the equilibrium moves to the left to get rid of extra heat.

Question 11

How can the pressure change the position of the equilibrium?

Answer 11

A(g) + B(g) == C(g)
- If the pressure is increased the equilibrium will move to the side with the fewest number of gas molecules to reduce the pressure.

Question 12

The Chemical equilibrium rule?

Answer 12

A chemical equilibrium will move to counteract any change imposed on it.

Question 13

Equation for the Bromine water experiment?

Answer 13

Br2(aq) +H2O(l) (yellow) == Br(aq) + OBr(aq) +H+(aq) (colorless)

Question 14

Ammonia to ammonia chloride reaction?

Answer 14

ammonia (NH3(g)) + hydrogen chloride (HCL(g)) == ammonium chloride (NH4Cl(s).

Question 15

Properties of Ammonia? NH3

Answer 15

• Colorless
• Colorless gas
• Vary soluble in water
• Pungent smell
• Gas at room temperature
• Base produces a solution of PH 10-11 when dissolved in water.

Question 16

Ammonia is needed and the starting material for which products?

Answer 16

Nitric acid and ammonia nitrate (a fertilizer)

Question 17

Main Equation for the Habour process?

Answer 17

nitrogen(N2(g)) + hydrogen(3H2(g)) == ammonia(2NH3(g))

Question 18

The reaction for the Habour process is endothermic or exothermic?

Answer 18

Exothermic. (delta)H = -80kJmol-1

Question 19

What is the catalyst used in the main Habour process reaction and why is it used?

Answer 19

• Iron catalyst is used.
• The catalyst (as with all reversible reactions) speeds up the reaction in both directions equally. So it simply reduces the amount of time taken to reach equilibrium.

Question 20

To increase yield in the Main Habour Process reaction we could?

Answer 20

• Increase the pressure.

- reduce the temperature.

Question 21

Conditions used for the main Habour Process reaction?

Answer 21

• Fe(Iron) Catalyst
• Pressure of 200 atm
• Temperature at 400o

Question 22

Why is 450o used in Main Habour Process Reaction?

Answer 22

This is a compromise, it is hot enough to enable that reaction to take place quickly but not too hot to ensure the equilibrium sits for enough towards the product.

Question 23

Why is 200atm used in Main Habour Process Reaction?

Answer 23

This is a compromise - it is high enough to increase yield but isent to expensive to maintain.

Question 24

How is H2 created in the Habour Process?

Answer 24

Obtained by reacting steam with CH4

Question 25

How is N2 created in the Habour Process?

Answer 25

Obtained for the air.

Question 26

What form is ammonia collected in?

Answer 26

NH3 is cooled and collected as a liquid.

Question 27

What does the statement 'that a reaction has reached equilibrium' mean?

Answer 27

Rate of forwards reaction = rate of backwards reaction.

Question 28

Why is nitrogen important for plants?

Answer 28

Nitrogen is needed for proteins in the leaves and stalks.

Question 29

If 80% of the air is nitrogen why can't plants use this?

Answer 29

This is because it needs to be in the form of nitric acid. In a soluble form.

Question 30

What happens when to much fertilizers are put on the fields?

Answer 30

Leaching occurs, Port from Biology, fertilizers in the water cause eutophication. Which causes other animals in the water to die.

Question 31

What happens when nitrates are ingested?

Answer 31

- Stomach cancer | - Blue Baby Syndrome, not enough oxygen in the blood to aid respiration.

Question 32

Step 1) in the production of H2SO4 - The Contact Process?

Answer 32

1) - Sulpher(S(s)) + Oxygen(O2(g)) = Sulpher dioxide(SO2(g))

Question 33

Step 2) in the production of H2SO4 - The Contact Process?

Answer 33

2) Sulpher dioxide(2SO2(g)) + Oxygen(O2(g)) = Sulpher monoxide(2SO3(g)) - Temperature used : 440oC - Catalyst used : V2O5 - High pressures are not needed as % conversion is already good enough.

Question 34

Step 3) in the production of H2SO4 - The Contact Process?

Answer 34

3) Sulpher monoxide(SO3(g)) + Water(H2O(l)) = Sulpheric Acid(H2SO4(l)) - diluted and sent to customers.

Question 35

Uses of Sulpheric Acid?

Answer 35

- Production of pharmaceuticals - Production of Paint, fertilizers and explosives - Used in metal treatment.

Question 36

In the Habour Process what will be present in the equilibrium mixture with ammonia?

Answer 36

- Un-reacted gasses ie. H2 and N2 will be present when the gasses are cooled and condense to a liquid. They are recycled before reaching the iron catalyst.

Question 37

In the Habour Process, How will the rate of reaction of nitrogen with hydrogen be affected by increasing the temperature.

Answer 37

The rate of reaction should increase because there is going to be more collisions between the atoms as the kinetic energy increases.

Question 38

What is seen when excess ammonia solution is added gradually to copper (II) chloride solution. With formula.

Answer 38

light blue precipitate darker blue solution [Cu(NH3)4(H2O)2]2+

Question 39

Nitric Acid? | Amonia?

Answer 39

HNO3 | NH3

Question 40

Explain why increasing the concentration of X has this effect on the rate of the reaction?

Answer 40

more particles more successful collisions. more frequently