Part 13 Industrial Chemistry Flashcards
What is meant by the term “initial rate” ?
Initial rate is the instantaneous rate of reaction at the start of a reaction.
State the raw material used in the chloralkali industry
Brine // concentrated / saturated NaCl solution
State one raw material for manufacturing vitamin C in industry.
Glucose
Why does the Haber process need natural gas as a raw material ?
Natural gas remains the more convenient / cheap way to provide hydrogen as feedstock for production of ammonia in the Haber process.
What is the advantage of recycling unconsumed hydrogen from chemical industry ?
Unconsumed hydrogen from chemical industries is allowed to react with carbon monoxide to form methanol. The conversion uses up the unconsumed hydrogen.
What is the advantage of using sugar as raw material ?
Sugar is renewable.
Explain why it is still needed to synthesise vitamin C industrially.
It is to solve the problems of inadequate or shrinking supply of vitamin C from natural resources.
State one feedstock for CaCO3(s).
Limestone // chalk // marble
What is meant by the term “activation energy” ?
Activation energy is the minimum kinetic energy that colliding particles must have for a collision to result in a chemical reaction.
What does the area under Maxwell-Boltzmann curve represent ?
The area under the curve represents the total number of particles in the gaseous system.
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.
An increase in temperature will increase the average kinetic energy of molecules. This will result in greater effective collisions per unit time. There is a larger portion of molecules will have kinetic energy greater than Ea.
State the Arrhenius equation
logK = logA - Ea/(2.3RT)
//
k = Ae^(-Ea/(2.3RT)
Suggest why catalyst can speed up a reaction.
A catalyst increases the rate of reaction by providing a alternative pathway with lower activation energy for the reaction to .
What is the importance of catalyst ?
Saves energy // the reaction can take place at lower temperature
Suggest one advantage of using porous structure in the catalytic converters.
It can increases the surface area of the catalyst so as to increase the effectiveness is the catalyst.
Explain why the effectiveness of catalyst may decrease after prolonged use(長時間使用).
Catalyst can be poisoned by impurities.
Explain why Haber process is important industrial process.
The Haber process produces ammonia which can make fertilisers to increase crop yield.
State the optimal operation temperature and pressure used in the Haber process.
400 - 450 ˚C 200atm
State the catalyst used in Haber process.
Finely divided iron
Suggest how nitrogen gas can be obtained in industry.
By fractional distillation of liquefied air
Suggest how Hydrogen can be obtained in industry.
Steam reforming of natural gas // cracking of naphtha // electrolysis of brine
Explain the use of drier in Haber process.
To prevent steam from reacting with Fe catalyst.
Explain why H2 and N2 need to be purified before going into the reaction chamber.
To remove sulphur and its compounds which would poison the catalyst.
Explain why there is a need to install a heat exchanger in chemical plant for Haber process.
The hot gas from reaction chamber can help heat up the hydrogen and nitrogen. It is to save energy.
Explain why the unreacted H2 & N2 are passed again to the reaction chamber.
To save reactants.
Write the overall equation for the electrolysis involved in the chloralkali industry.
2NaCl + 2H2O —> 2NaOH + Cl2 + H2
What is the anode of Flowing mercury cell ?
Titanium // graphite
What is the cathode of flowing mercury cell ?
Flowing mercury
What is the electrolytes of flowing mercury cell ?
Brine
What is the anode of membrane cell ?
Titanium
What is the cathode of membrane cell ?
Nickel
What is the electrolyte of membrane cell ?
Brine
Give two advantages of a membrane electrolytic cell over a flowing mercury cell in chloroalkali industry.
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.
Suggest a potential hazard for storing methanol.
Toxic // flammable
Why is methanol an important compound in the chemical industry ?
Methanol is important because it is a 1-carbon compound and acts as a starting material to make organic compounds with larger carbon numbers.
Suggest a source of methane.
Biomass // natural gas
State the condition and required and catalyst used for production of methanol from syngas.
Catalyst : Cu // ZnO // Al2O3
Condition : 200 - 300 ˚C 50 - 100 atm
State the catalyst used and required conditions in production of syngas.
Catalyst : NiO
Conditions : 700-1000 ˚C 100 atm
Give 4 principles of green chemistry.
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
Comment on this statement : “A reaction with a high atom economy should also have a high yield.”
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.
What is brine ?
Saturated / concentrated NaCl
