2.6 Reversible Reactions Industrial Process And Important Chemicals

Question 1

What is a reversible reaction?

Answer 1

The reaction that happens in both directions, the products of the reaction can react together to produce the original reactants

Question 2

If the forward reaction is exothermic, what is the reverse reaction?

Answer 2

Endothermic

Question 3

What is the Haber process

Answer 3

used in the industrial production of ammonia

Question 4

equation for the Haber process

Answer 4

nitrogen + hydrogen –> ammonia

N2(g) + 3H2(g) <==> 2NH3(g)

Question 5

How is ammonia collected Haber process

Answer 5

By cooling the reaction so the ammonia condenses into a liquid

Question 6

What happens to the unreacted nitrogen and hydrogen in the Haber process

Answer 6

They are recycled back, so there is no waste

Question 7

Conditions of the Haber process

Answer 7

a higher temp – 450°C - very high temp = lower yield and expensive BUT very low temp = higher yield BUT lower rate of reaction therefore 450 = compromise
a high pressure – 200 atmospheres - higher pressure = higher yield BUT higher costs & risk of explosion
an iron catalyst - used to speed up rate of reaction (compromise)

Question 8

Stage one of Haber process (BBC Bitesize)

Answer 8

Having obtained the hydrogen and nitrogen gases (from natural gas and the air respectively), they are pumped into the compressor through pipes.

Question 9

Stage 2 Haber process (BBC Bitesize)

Answer 9

The gases are pressurised to about 200 atmospheres of pressure inside the compressor.

Question 10

Stage 3 Haber process (BBC Bitesize)

Answer 10

The pressurised gases are pumped into a tank containing beds of iron catalyst at about 450°C. In these conditions, some of the hydrogen and nitrogen will react to form ammonia.

Question 11

Stage 4 Haber process (BBC Bitesize)

Answer 11

The unreacted nitrogen and hydrogen, together with the ammonia, pass into a cooling tank. The cooling tank liquefies the ammonia, which can be removed into pressurised storage vessels.

Question 12

Stage 5 Haber process (BBC Bitesize)

Answer 12

The unreacted hydrogen and nitrogen gases are recycled by being fed back through pipes to pass through the hot iron catalyst beds again

Question 13

Test for ammonia

Answer 13

Ammonia gas will change damp red litmus paper blue!

Question 14

Test for ammonium ion

Answer 14

1 - add sodium hydroxide
2 - Test the gas given off
The ammonium ions convert into ammonia gas which turns the damp red litmus paper blue

Question 15

4 stages of the contact process (manufacturing sulfuric acid)

Answer 15

1. Sulfur burns in air to form sulfur dioxide gas
2. Sulfur dioxide reacts with oxygen to forms sulfur trioxide gas
3. Sulfur trioxide is dissolved in concentrated sulfuric acid to produce oleum
4. The oleum is then diluted with water to produce sulfuric acid

Question 16

Why is sulfur dioxide not directly added to water

Answer 16

The reaction is too violent!!

Question 17

Chemical equations of the 4 stages of the contact process

Answer 17

1. The manufacture of sulfur dioxide
   Sufur + oxygen –> sulfur dioxide
   S + O2 –> SO2
2. The conversion of sulfur dioxide to sulfur trioxide - a reversible reaction
   sulfur dioxide + oxygen <==> sulfur trioxide
   SO2 + O2 <==> 2SO3
3. Dissolving sulfur trioxide in concentrated sulfuric acid
   Sulfuric acid + sulfur trioxide –> oleum
   H2SO4 + SO3 –> 2H2S2O7
4. Oleum diluted with water - to make sulfuric acid
   Oleum + water –> sulfuric acid
   H2S2O7 + H2O –> 2H2SO4

Question 18

Conditions used at the reversible reaction of sulfur dioxide and oxygen to make sulfur trioxide

Answer 18

400-500 degrees C
Atmospheric pressure
Vanadium (VI) oxide catalyst

Question 19

What does sulfuric acid do
Example with glucose
what type of reaction

Answer 19

It can be used as a dehydrating agent - removes water from a substance
Concentrated sulfuric acid takes away the elements of water leaving only carbon
C6H12O6 –> 6C(s) + H2O
water is removed as steam as reaction is exothermic

Question 20

Uses of sulfuric acid

Answer 20

Fertilisers
Paints
Fibres
Detergents
Plastics
Dehydrating agent

Question 21

What are the reaction conditions for a process a compromise between
Examples (Haber process)

Answer 21

Yield of production, rate of production, cost and safety
e.g. rate too slow at low temp; higher temp is a compromise between yield and rate
Higher pressures = expensive, risk of explosions - compromise between yield and cost/safety

Question 22

Name of a common fertiliser and how it’s made

Answer 22

Ammonium sulfate - made by neutralising (add base) sulfuric acid (or other e.g. nitric - will make ammonium nitrate) with ammonia or ammonium hydroxide
With ammonia: 2NH3 + H2SO4 –> (NH4)2SO4
With ammonium hydroxide: 2NH4OH + H2SO4 —> (NH4)2SO4 + 2H2O

Question 23

Advantages of fertilisers

Answer 23

Increases crop yield
Healthier crops
Improve soil quality

Question 24

Disadvantages of fertilisers

Answer 24

Eutrophication
Risk of stomach cancer
Blue baby syndrome ((low oxygen levels in the blood))

Question 25

how is nitrogen collected for the Haber process

Answer 25

from air

Question 26

how is hydrogen collected for the Haber process

Answer 26

From natural gas (reacting steam with methane)