3.2 - Reversible reactions, Industrial Processes And Important Chemicals

Question 1

What are the raw materials needed for the Haber process?

Answer 1

• air which supplies the nitrogen
• iron (catalyst)
• natural gas (methane), and water which supplys the hydrogen and energy needed to heat the reactants

Question 2

What is the word and symbol equation of making ammonia?

Answer 2

Nitrogen + hydrogen = ammonia

N2 + 3H2 = 2NH3

Question 3

Why is a medium temperature with a medium pressure used?

Answer 3

• a high pressure would produce more yield, but would be too expensive
• yield of ammonia would be better at lower temps but this results in a slower reaction
• compromise
• catalyst speeds up reaction

Question 4

Why would the yield of ammonia be better at lower temps?

Answer 4

-the forward reaction is exothermic so increasing the temp will move the equilibrium towards nitrogen & hydrogen and away from ammonia

Question 5

Why are the unreacted nitrogen and hydrogen gases recycled?

Answer 5

Because it is more efficient to re-use and it reduces the quantity of raw materials needed

Question 6

How can nitric acid be formed by ammonia?

Answer 6

• ammonia can be burnt in oxygen to form nitrogen monoxide

- this can be put over a catalyst to form nitrogen dioxide = nitric acid

Question 7

What does it mean that sulfuric acid acts as a dehydrating agent?

Answer 7

It removes the elements oxygen and hydrogen from compounds

Question 8

Explain the 3 stages for the ‘contact process’ to make sulfuric acid

Answer 8

1. Sulphur + oxygen = sulfur dioxide
2. Sulfur dioxide is oxidised to a sulfur trioxide by reacting it with excess air over a vanadium oxide catalyst at 420 celsius at pressures not much above atmospheric
3. Sulfur trioxide is absorbed in sulfuric acid. The sulfur trioxide reacts with a small quantity of water to form a sulfuric acid

Question 9

Why can’t sulfur trioxide be absorbed in 100% water?

Answer 9

The reaction is too violent and produces a mist of the acid

Question 10

What are the word and symbol equations to form sulfur dioxide?

Answer 10

Sulfur dioxide + oxygen = sulfur trioxide

2SO2 + O2 = 2SO3

Question 11

What are the advantages of using nitrogenous fertilisers for individuals, communities and the environment?

Answer 11

Ind: cheap to buy
Comm: increased crop yield can ease world hunger
Environment: replaces lost minerals on the soil, improves soil fertility

Question 12

What are the disadvantages to an individual, community and environment when using nitrogenous fertilisers?

Answer 12

Ind: lots of controversy as can get into water supply
Comm: nitrates can cause cancer
Environ: eutrophication which can kill fish

Question 13

What are the advantages and dis of using nitrogenous fertilisers for crop growth?

Answer 13

Ad:

• increases crop yields
• relatively cheap
• healthier plants
• improves poor quality land

Dis:

• blue baby syndrome
• eutrophication

Question 14

What are the observations with sugar + concentrated sulphuric acid?

Answer 14

• STEAM RISING- sugar is being dehydrated
• SUGAR TURNS BLACK - h and O are being removed so only carbon is left which is black
• CARBON RISES OUT OF BEAKER - the steam gets trapped in the carbon and acts like a raising agent

Question 15

Describe the Haber process to make ammonia

Answer 15

• high temp, low pressure
• hydrogen and atmospheric nitrogen react to form ammonia. It is reversible so can go forwards or backwards depending on the conditions