Part 13 Industrial Chemistry

Question 1

What is meant by the term “initial rate” ?

Answer 1

Initial rate is the instantaneous rate of reaction at the start of a reaction.

Question 2

State the raw material used in the chloralkali industry

Answer 2

Brine // concentrated / saturated NaCl solution

Question 3

State one raw material for manufacturing vitamin C in industry.

Answer 3

Glucose

Question 4

Why does the Haber process need natural gas as a raw material ?

Answer 4

Natural gas remains the more convenient / cheap way to provide hydrogen as feedstock for production of ammonia in the Haber process.

Question 5

What is the advantage of recycling unconsumed hydrogen from chemical industry ?

Answer 5

Unconsumed hydrogen from chemical industries is allowed to react with carbon monoxide to form methanol. The conversion uses up the unconsumed hydrogen.

Question 6

What is the advantage of using sugar as raw material ?

Answer 6

Sugar is renewable.

Question 7

Explain why it is still needed to synthesise vitamin C industrially.

Answer 7

It is to solve the problems of inadequate or shrinking supply of vitamin C from natural resources.

Question 8

State one feedstock for CaCO3(s).

Answer 8

Limestone // chalk // marble

Question 9

What is meant by the term “activation energy” ?

Answer 9

Activation energy is the minimum kinetic energy that colliding particles must have for a collision to result in a chemical reaction.

Question 10

What does the area under Maxwell-Boltzmann curve represent ?

Answer 10

The area under the curve represents the total number of particles in the gaseous system.

Question 11

With reference to the Maxwell-Boltzmann curve, suggest why an increase in temperature can lead to an increase in the reaction rate of gaseous reaction.

Answer 11

An increase in temperature will increase the average kinetic energy of molecules. This will result in greater effective collisions. There is a larger portion of molecules will have kinetic energy greater than Ea.

Question 12

State the Arrhenius equation

Answer 12

logK = logA - Ea/(2.3RT)
//
k = Ae^(-Ea/(2.3RT)

Question 13

Suggest why catalyst can speed up a reaction.

Answer 13

A catalyst increases the rate of reaction by providing a alternative pathway with lower activation energy for the reaction to .

Question 14

What is the importance of catalyst ?

Answer 14

Saves energy // the reaction can take place at lower temperature

Question 15

Suggest one advantage of using porous structure in the catalytic converters.

Answer 15

It can increases the surface area of the catalyst so as to increase the effectiveness is the catalyst.

Question 16

Explain why the effectiveness of catalyst may decrease after prolonged use(長時間使用).

Answer 16

Catalyst can be poisoned by impurities.

Question 17

Explain why Haber process is important industrial process.

Answer 17

The Haber process produces ammonia which can make fertilisers to increase crop yield.

Question 18

State the optimal operation temperature and pressure used in the Haber process.

Answer 18

400 - 450 ˚C 200atm

Question 19

State the catalyst used in Haber process.

Answer 19

Finely divided iron

Question 20

Suggest how nitrogen gas can be obtained in industry.

Answer 20

By fractional distillation of liquefied air

Question 21

Suggest how Hydrogen can be obtained in industry.

Answer 21

Steam reforming of natural gas // cracking of naphtha // electrolysis of brine

Question 22

Explain the use of drier in Haber process.

Answer 22

To prevent steam from reacting with Fe catalyst.

Question 23

Explain why H2 and N2 need to be purified before going into the reaction chamber.

Answer 23

To remove sulphur and its compounds which would poison the catalyst.

Question 24

Explain why there is a need to install a heat exchanger in chemical plant for Haber process.

Answer 24

The hot gas from reaction chamber can help heat up the hydrogen and nitrogen. It is to save energy.

Question 25

Explain why the unreacted H2 & N2 are passed again to the reaction chamber.

Answer 25

To save reactants.

Question 26

Write the overall equation for the electrolysis involved in the chloralkali industry.

Answer 26

2NaCl + 2H2O —> 2NaOH + Cl2 + H2

Question 27

What is the anode of Flowing mercury cell ?

Answer 27

Titanium // graphite

Question 28

What is the cathode of flowing mercury cell ?

Answer 28

Flowing mercury

Question 29

What is the electrolytes of flowing mercury cell ?

Answer 29

Brine

Question 30

What is the anode of membrane cell ?

Answer 30

Titanium

Question 31

What is the cathode of membrane cell ?

Answer 31

Nickel

Question 32

What is the electrolyte of membrane cell ?

Answer 32

Brine

Question 33

Give two advantages of a membrane electrolytic cell over a flowing mercury cell in chloroalkali industry.

Answer 33

No toxic mercury will be produced by membrane electrolytic cell but toxic mercury may leak out from flowing mercury cell.
Energy required for a membrane electrolytic cell is less than that for a flowing mercury cell.

Question 34

Suggest a potential hazard for storing methanol.

Answer 34

Toxic // flammable

Question 35

Why is methanol an important compound in the chemical industry ?

Answer 35

Methanol is important because it is a 1-carbon compound and acts as a starting material to make organic compounds with larger carbon numbers.

Question 36

Suggest a source of methane.

Answer 36

Biomass // natural gas

Question 37

State the condition and required and catalyst used for production of methanol from syngas.

Answer 37

Catalyst : Cu // ZnO // Al2O3
Condition : 200 - 300 ˚C 50 - 100 atm

Question 38

State the catalyst used and required conditions in production of syngas.

Answer 38

Catalyst : NiO
Conditions : 700-1000 ˚C 100 atm

Question 39

Give 4 principles of green chemistry.

Answer 39

Waste prevention
Maximising atom economy
Use less hazardous chemical
Producing safer product
Using safer solvent
Energy efficiency
Using renewable raw materials
Reducing derivatives
Using catalysts
Designing degradable product

Question 40

Comment on this statement : “A reaction with a high atom economy should also have a high yield.”

Answer 40

The calculation of atom economy is based on a 100% completed reaction. Thus a reaction with high atom economy does not necessarily have a high yield.

Question 41

What is brine ?

Answer 41

Saturated / concentrated NaCl