C4-C6 Questions

Question 1

Suggest other factors, apart from atom economy, that must be considered when deciding which reaction pathway to choose for the manufacture of hydrogen.

Answer 1

Percentage yield
Usefulness of by products
Cost of Raw Materials

Question 2

What is a catalse?

Answer 2

Catalase is an enzyme in the liver which breaks down harmful hydrogen peroxide into oxygen and water.

Question 3

What are the problems called by mineral deficiency:
Nitrogen
Phosphorus
Potassium

Answer 3

Nitrogen causes poor growth and yellow leaves
Phosphorus causes poor growth and discoloured leaves
Potassium cause poor fruit growth and discoloured leaves

Question 4

Describe how scientists think an oxygen rich atmosphere developed over time.

Answer 4

As earth could water vapour condensed to form oceans.
Leaving initial atmosphere of CO2
Photosynthetic organisms began to make O2 so reduces CO2 amount
Increase in oxygen and nitrogen levels.

Question 5

Describe the enhanced greenhouse effect and the problems it may cause

Answer 5

CO2 is released into the atmosphere by the combustion of fossil fuels
Methane is released into the atmosphere from paddy fields and cattle.
Additional greenhouse gases by human causes enhanced greenhouse effect.
It can cause ice caps/glacials to melt as well as a change in global temperature.

Question 6

What is bioleaching?

Answer 6

A method of extraction for low grade ore.
Bacteria oxidise Iron (II) and sulfide to produce sulphuric acid. This acid can be used to extract copper from copper ores

Question 7

Write about the advantages and disadvantages of bleaching of bioleaching

Answer 7

Advantages is that it is cheaper , low grade ore can be used, bacteria occur naturally.
Disadvantages - very slow

Question 8

Describe how plants are used in phytoextraction to extract metals.

Answer 8

Plants absorb dissolved ions through their roots
Metal ions accumulate in roots / shoots / leaves
Crop is planted in soil containing a low-grade ore
A ‘complexing agent’ is added so the plants absorb the metal ions more easily
Plants (are harvested and) burnt to produce an ash with high concentration of the metal
Metal is extracted from ash

Question 9

Phytoextraction is a more carbon neutral activity than traditional mining. Explain why

Answer 9

Burning plants release CO2 but plant absorb CO2 for photosynthesis

Question 10

What are the stages for life cycle assesment

Answer 10

Extract raw materials
Manufacture from raw material
Transport
Dispose

Question 11

Describe the four processes and how the greenhouse effect occurs.

Answer 11

radiation/heat from the Sun reaches the (surface of the) Earth

radiation is absorbed by the (surface of the) Earth

some energy/heat or infrared (radiation) go back into space

some energy/heat or infrared (radiation) is absorbed/trapped by greenhouse gas (molecules) in the (Earth’s) atmosphere

Heat from greenhouse gas (molecules) returns to Earth warming the (surface of the) Earth

Question 12

A student has an unknown solution. She thinks that the solution contains Copper II ions and bromide ions.
Describe the chemical tests she does this to confirm the presence of the two ions in the solution.

Answer 12

Copper (II) ions can be tested by using sodium hydroxide, and if present it will be a blue precipitate.
Bromide ions can be tested by using aqueous silver nitrate and dilute nitric acid. It gives a cream precipitate.

Question 13

What is meant by the term dynamic equilibrium ?

Refer to both concentrations and rate of reaction in your answer.

Answer 13

Dynamic equilibrium is when the rate of the forward reaction is equal to the rate of the backward reaction.
Concentration of reactants and products do not change.

Question 14

The Haber process is used to manufacture ammonia. Explain the importance of the Haber process in agriculture.

Answer 14

Endless supply of starting material as Haber Process turns atmospheric nitrogen into ammonia.
Ammonia is used to make fertiliser which increases crop yield.

Question 15

What are the conditions used for Contact Process?

Answer 15

450 degrees
normal atmospheric pressure or 10 atm
Vanadium Pentoxide catalyst

Question 16

What is needed for corrosion

Answer 16

Contact with oxygen and water

Question 17

Describe what observations you would make when a small piece of potassium is added to a trough of water.

Answer 17

Potassium moves around rapidly on the surface of the water. The gas would ignite and produce a lilac flame.

Question 18

What are the proportion of gases in the present day

Answer 18

Nitrogen - 78%
Oxygen - 21%
CO2 - 0.04%

Question 19

Describe how the percentages of the gases in the atmosphere have changed between 3 billion years ago and 2 billion years ago.

Answer 19

The amount of nitrogen has dropped because the levels of oxygen increased.
There was no oxygen 3 billion years ago but 2 billion years ago 10% of the atmosphere was oxygen due to photosynthesising plants.
The amount of carbon dioxide remained relatively constant due to volcanic activity.

Question 20

2 disadvantage of phytoextraction

Answer 20

Very slow and burning plants can release contamination.

Question 21

How to test for carbonate ions.

Answer 21

Add hydrochloric acid - bubbles are formed.

Test the gas given off for CO2 by passing it into limewater. If turns cloudy CO2 is present.

Question 22

What is contact process and what are the equations.

Answer 22

Contact process is used for making sulphuric acid. 
S + O2 --> SO2
2SO2 + O2 --> 2SO3
H2O + SO3 --> H2SO4 
but SO3 is hazardous so 
H2SO4 + SO3 --> H2S2O7 (oleum) 
H2S2O7 + H2O --> 2H2SO4

Question 23

What are the conditions used for Haber Process?

Answer 23

200 atmospheres
450 degrees
iron catalyst

Question 24

What is the formula for haber process

Answer 24

N2 + 3H2 –>–< 2NH3

Question 25

What happens in the blast furnace when extracting iron.

Answer 25

Coke burns with hot air 
C + O2 —> CO2 
Coke reduces CO2 
C + CO2 —> 2CO
Carbon monoxide reduce iron oxide to iron
3CO + Fe2O3 —> 3CO2 + 2Fe

Impurities of iron ore is removed
CacO3 —> CaO + CO2
Slag is produced (impurities)
CaO + SiO2 —> CaSiO3

Question 26

What are ceramics?

Answer 26

Ceramics are hard non metallic materials
High melting points
Hard and stiff but brittle
Poor conductors

Question 27

What are composite materials?

Answer 27

Made from two or more materials combined together each with different properties.

Question 28

How is fresh water treated?

Answer 28

Water passes through a screen, they catch large objects such as leaves
In the settlement tanks , sand and soil settle out
Aluminium sulfate and lime are added to water so small particles can clump together
Water is passed through filter made of sand, to remove any remaining dirt
Small amount of chlorine is added to kill bacteria, ph is checked (7)
Water is stored in large tanks ready to be used

Question 29

G/dm^3 to mol/dm^3

Answer 29

Conc g/dm^3 / RFM of solute