Questions Corrections 2021

Question 1

Plan an investigation to determine the Rf value for the dye in the food colouring

Answer 1

1) Draw pencil line on chromatography paper
And place spot of food colouring on start line
2) Use a solvent such as water
3) Place solvent in beaker and chromography paper in the solvent but solvent is below start line
4) Use a lid and wait for the solvent to travel up paper
Mark solvent front and dry chromatography paper
5) Measure distance between start line and centre of spot and measure distance between start line and solvent front
6) Use measurements to determine Rf value

Question 2

Why did the students results for the chromatography experiment differ

Answer 2

Different solvent used

Question 3

Suggest why polyethene is easier to recycle than thermosetting polymers

Answer 3

Melts
So can be reshaped

Question 4

How can different forms of polyethene be produced from ethene

Answer 4

Use different reaction conditions

Question 5

Explain why high density polyethene is more dense than low density polyethene

Answer 5

Polymer chains are closer together
So more atoms per unit volume

Question 6

Name the soluable salts produced when calcium phosphate reacts with

nitric acid
Phosphoric acid

Answer 6

Calcium nitrate
Calcium triple superphosphate

Question 7

Give a test to identify the Group 1 metal ion in potash alum and the result

Answer 7

Flame test
Lilac flame

Question 8

Give the result of the test for the solution of potash alum by adding sodium hydroxide solution until a change is seen

Answer 8

White precipitate

Question 9

What is an additional step to identify other metal ions in the potash alum as they all give the same result

Answer 9

Add excess sodium hydroxide
So the precipitate dissolves

Question 10

Suggest three reasons why recycling scrap copper is a more sustainable way of obtaining copper than processing copper ores

Answer 10

Recycling conserves copper ores
Recycling uses less energy
Recycling reduces waste

Question 11

Describe how copper is extracted from low grade ores by phytomining

Answer 11

Grow plants on land containing copper ores
Plants are burnt to produce ash
Ash dissolved in acid
Electrolysis of solution

Question 12

Two reasons why phytomining has not been widely used to extract copper

Answer 12

High grade ores still available
Land not available

Question 13

Name the process used to produce ethene from large hydrocarbon molecules

Answer 13

Cracking

Question 14

Describe the conditions used to produce ethene from large hydrocarbon molecules

Answer 14

High temperature
Catalyst

Question 15

Explain how the conditions for this reaction should be chosen to produce ethanol as economically as possible

Ethene plus steam equals ethanol
(Forward reaction exothermic)
(More molecules on the left hand side)

Answer 15

Higher temperature gives higher rate because more frequent collisions
Higher pressure gives higher rate
A catalyst can be used to give a higher rate as the activation energy is reduced
Higher temperature gives lower yield as reaction is exothermic
Higher pressure gives higher yield as there are less molecules on left hand side

Higher temp uses more energy so costs increase and higher pressure also causes increase cost

So chosen temperature is a compromise between rate and yield and so is pressure a compromise

Question 16

Suggest the reaction conditions needed to produce butane from sugar solution by adding bacteria

Answer 16

Warm
Anaerobic conditions