Using Resources

Question 1

Suggest two reasons why recycling scrap copper is more sustainable than extracting copper from copper ores. [2 marks]

Answer 1

any two from:
(recycling scrap copper)
* uses less energy
* conserves copper (ore)
* (produces) less waste / less landfill required
* specified environmental impact

ignore references to cost

Question 2

What is different about water after having been treated by reverse osmosis?

Answer 2

The salty water is passed through a membrane that only allows water molecules to pass through.
Ions & larger molecules are trapped by the membrane and so separated from the water - the water has lower ion concentrations.

Question 3

After treatment the ground water is sold by a company as pure water.
The ground water is not chemically pure because the water contains sodium ions and chloride ions.
Suggest what the company means by ‘pure’. [1 mark]

Answer 3

(the water is) unadulterated
or
(the water is) in its natural state

allow nothing is added (to the water)
allow (the water) contains no microbes

Question 4

Give the sources of the nitrogen and of the hydrogen used in the Haber process. [2 marks]

Got 1/2 marks in Easter holiday.

Answer 4

(nitrogen) air / atmosphere
(hydrogen) natural gas / methane / water / steam

Question 5

This diagram represents the Haber process: https://cdn.discordapp.com/attachments/1062056354874937405/1225487420716220526/image.png?ex=66214f19&is=660eda19&hm=2b676082eef55435f9e1010c5626f2a25b57eeeedb0b4ea99828a74878ad62f5&
Explain how the ammonia produced is separated from the unreacted nitrogen and hydrogen in X. [2 marks]

Got 0/2 marks in the Easter holiday.

Answer 5

(mixture is) cooled
(so that only) ammonia liquefies / condenses

Question 6

The equation for the production of ammonia in the Haber process is:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
The forward reaction is exothermic.
The conditions used are:
* a temperature of 450 °C
* a pressure of 200 atmospheres
* the presence of an iron catalyst.
Explain why these conditions are chosen for economical production of ammonia in the Haber process.
You should include references to the rate of reaction and the position of equilibrium. [6 marks]

Got 4/6 marks in the Easter holiday.

Answer 6

rate
* higher temperature gives higher rate because of more frequent collisions
* higher temperature gives higher rate because more particles have the activation energy
* higher pressure gives higher rate because of more frequent collisions
* use of catalyst gives higher rate because the activation energy is lowered

equilibrium
* higher temperature shifts the position of equilibrium to the left because reaction is exothermic
* higher pressure shifts the position of equilibrium to the right because more molecules on left-hand side
* use of catalyst has no effect on the position of equilibrium

other factors
* higher temperature (than 450°C) uses more energy so increases costs
* higher pressure (than 200 atmospheres) uses more energy so increases costs
* higher pressure (than 200 atmospheres) requires stronger reaction vessels so increases costs
* use of a catalyst reduces energy costs

compromise
* the temperature chosen is a compromise between rate of reaction and position of equilibrium
* the temperature chosen is a compromise between rate and cost
* the pressure chosen is a compromise between yield / rate and cost

Level marked - 3 levels.