Chem

Question 1

Explain why air needs to be replaced with argon gas for the reduction of titanium chloride

Answer 1

Oxygen in the air reacts with titanium
This makes titanium brittle

Question 2

Give reasons why electrolysis will be more efficient method of extraction than kroll process

Answer 2

Has fewer stages
Uses a lower temperature
Uses less chemicals
Gives a higher yield

Question 3

Compare similarities and differences between extraction of aluminium and extraction of chlorine by electrolysis (6 marks)

Answer 3

Similarities
-elements are formed at the cathode and anode
-Ions are free to move in both compounds
-Both raw materials are ionic compounds

Differences
-Alumina is an oxide but brine is a chloride
-Electrolysis of alumina requires more energy than brine
-Electrolysis of brine uses a membrane
-No ions are left behind in the electrolysis of alumina

Question 4

Describe how the water molecules are bonded to the vanadium iron

Answer 4

Dative Covalent bond from water to vanadium ion

Question 5

Describe how the ultraviolet light causes the reaction to begin

Answer 5

Breaks the bromine bond from the free radical form atom has a single electron

Question 6

Describe the process of sp2 hybridisation for a carbon atom

Answer 6

There is 1 S orbital and 2 P orbitals involved they mix
Each orbital holds one unpaired electron
The energy level of the S orbital increases
The hybrid orbitals are identical

Question 7

Describe where each product is formed during the electrolysis of brine

Answer 7

Hydrogen is formed at the cathode
Chlorine is formed at the anode
Sodium hydroxide is left behind in the solution and it remains behind in the cell

Question 8

Discuss the advantages and disadvantages of the manufacture of ethanol by the hydration of ethene (6 marks)

Answer 8

Advantages
-All reactants used up to form ethanol
-Raw material is easy to obtain
-Higher temperature, so quicker reaction

Disadvantages
-It’s a reversible reaction, so there will not be 100% yield of ethanol
-High temperature so greater cost
-It’s nonrenewable as it uses fossil fuels. This is bad for the environment.

Question 9

Explain how transition metal often works as catalyst

Answer 9

Speeds up the reaction
Provides an alternative route with a lower activation energy
Transition meals change oxidation state

Question 10

Explain how the carbon to carbon bond strength in ethane is different to ethene

Answer 10

-Only a single bond in ethane
-So Ethane has the longer chain
Ethane is weaker, so it is easier to break
-More electrons are shared between the two carbon atoms in the ethene
-atoms in the ethene.

Question 11

Explain how the diaphragm cell is used to produce sodium hydroxide, chlorine and hydrogen (6 marks)

Answer 11

-Brine is sodium chloride
-Contains sodium ions, chloride ions, hydrogen ions and hydroxide ions
Ions are free to move the solution and carry electrical charge
-Negative Chloride ions attracted to the positive anode
-The sodium and hydroxide ions are left in the solution. This forms HCl
-Sodium hydroxide and chlorine react together to form sodium chlorate
-Diaphragm separate sodium hydroxide from chlorine so that they do not react together

Question 12

Explain the difference in bond length between a carbon-carbon double bond and a carbon-carbon single bond

Answer 12

A double bond is shorter than a single bond
There are more electrons in a double bond
This is a two carbon atoms closer together

Question 13

Explain the effect of using a catalyst in the haber process

Answer 13

Speeds up the reaction and provides a surface area for the particles to react upon

Bonds within the reactant particles are weakened

More collisions

Question 14

Electrolysis of brine can be carried out in a membrane cell

Explain the function of the membrane cell

Answer 14

Membrane keeps chlorine gas separate from the sodium hydroxide

Chlorine will not be able to react with the hydrogen

The membrane is not allow negative ions to pass through

Sodium hydroxide solution higher purity

Question 15

Explain the three stages of the three radical mechanism involved in the formation of chloromethane (6)

Answer 15

It is a chain reaction
Initiation is the first stage the UV light provide energy for the reaction
Forms Free radicals
Propagation is the next stage
Chlorine radical removes the hydrogen from the methane, and this forms a methyl radical
The chlorine free radical removes the hydrogen from another methane
Termination is the end of the reaction
To me, feel of radical reacts with the chlorine radical to form chloromethane
Methyl radical react to form Ethane

Question 16

Explain why Alumina must be dissolved before electrolysis can take place

Answer 16

To allow ions to move so the ions can carry the electrical current during the electrolysis

Question 17

Give two reasons why electrolysis of alumina is expensive

Answer 17

Large amount of energy is required to maintain high temperature to dissolve the alumina

Large amount of electricity is required for electrolysis

Question 18

Why benzene cannot be an alkene

Answer 18

Benzene has the same number of hydrogen as carbons
Benzene does not have 12 hydrogen atoms

Question 19

Explain why manganese oxide can act as a catalyst

Answer 19

It has incomplete d subshell
It can accept or lose electrons
And this means it can be oxidised or reduced to back again to its original form
It lowers activation energy

Question 20

The extraction of titanium from its ore uses two redox reactions

Answer 20

Carbon is oxidised
Chlorine is reduced
Titanium and oxygen is not reduced or oxidised in this reaction so there is no change in oxidation number

Titanium is reduced
Magnesium is oxidised
Magnesium displace, titanium
Chlorine is not oxidised or reduced in this reaction