2022 p2

Question 1

suggest why poly(butene) insulation must be removed from copper wire before copper is recycled

Answer 1

because copper eould be contaminated/impure

Question 2

Explain how fractions are obtained from fractional distillation

Answer 2

-crude oil heated to vaporise
-there is a temperature gradient in the column
-gases condense at different levels
-because of their different boiling points

Question 3

Justify why thinking heavy fuel oil is more viscous than kerosene is correct

Answer 3

-as molecular size increases, viscositt increases
-and heavy fuel oil has larger molecules than kerosene

Question 4

test for alkenes

Answer 4

bromine water turns brown -> colourless

Question 5

Describe how sewage is treated to remove organic matter

Answer 5

-Screening and grit removal ( to remove large insoluble solids)
-sedimentation (to produce sewage slude and effluent)

-anaerobic DIGESTION of sewage sludge
-aerobic dugestion/aerobic biological treatment of effluent

Question 6

what do companies mean by ‘pure’ water

Answer 6

nothing added to water

Question 7

Describe how deposits of natural gas are formed

Answer 7

-plankton died

-organisms were covered by sediments (buried in anaerobic conditions)

-subjected to high temp AND high pressure

(over millions of years)

Question 8

Give sources of the nitrogen and hydrogen used in the haber process

Answer 8

nitrogen: air
hydrogen: natural gas

Question 9

Explain how ammonia produced in haber process is separated from unreacted nitrogen and hydrogen

Answer 9

it is cooled
and condensed/ liquified

Question 10

Explain why these conditions are chosen for economical production of ammonia is Haber process:

-temp of 450 degrees
-pressure of 200 atmospheres
-presence of iron catalyst

(talk ab rate and equilibrium)
[6 marks]

Answer 10

temp:
-higher temp gives higher rate because more frequent collisions and more particles have activation energy (as kinetic energyis higher)
-higher temp shifts equilibrium left as reaction is exothermic
-higher temp uses more energy so increases cost
-the temp chosen is a compromise between rate and equilibrium position
-temp chosen is compromise between rate and cost

pressure:
-higher pressure gives higher rate because more frequent collisions
-shifts position of equilibrium to right because more molecules on left hand side
-higher pressure .uses more energy so increases costs
-higher pressure requires stromger reaction vessels so increases costs
-pressure chosen is compromise between yield/rate and costs

catalyst:
-use of catalyst lowers AE so gives higher rate
-does not effect position of equilibrium