Aluminium ore which is called bauxite is purified by the Bayer Process.The ore is mixed with a hot concentrated solution of sodium hydroxide. The sodium hydroxide dissolves the oxides of aluminum and silicon and leaving other impurities including iron oxides as solid.The mixture is then filtrated to remove the insoluble impurities.The filtrate which now contains the oxides of aluminum and silicon is treated by bubbling carbon (iv)oxide gas through the solution.The Carbon (iv)oxide forms weak acidic solution of carbonic acid that then neutralizes the sodium hydroxide from the first treatment. The treatment by neutralization will also selectively precipitate the aluminum oxide and leave the silicate in solution.The mixture is then filtrated to separate it.Thereafter,the purified aluminum oxide is heated to evaporate the water yielding a white powder, aluminium oxide, from which aluminium can be extracted. Aluminium oxide having a very high melting point (over 2,000°C),it is mixed with cryolite, a mixture of sodium fluoride and aluminum fluoride, and heated to about 980 degrees Celsius to melt the solids. The mixture melts at a much lower temperature than aluminum oxide would by itself. The use of cryolite reduces some of the energy costs involved in extracting aluminium as it lowers the melting point.The hot molten mixture is then electrolyzed.Aluminum ions are reduced to Aluminium metal that forms at the negative electrode(cathode) and sinks to the bottom of the tank, where it is tapped off. At the anode, oxygen is produced from the oxide ions.Both the anode and cathode materials are carbon in the form of graphite, which also is oxidized and must be replaced quite frequently.
Mr Masinde answered the question on April 24, 2018 at 15:50
- Write chemical equation for reaction between dry hydrogen gas and heated lead (ii) oxide(Solved)
Write chemical equation for reaction between dry hydrogen gas and heated lead (ii) oxide.
Date posted: April 21, 2018. Answers (1)
- (i) What is rusting?
(ii) Give the chemical name of rust.(Solved)
(i) What is rusting?
(ii) Give the chemical name of rust.
Date posted: April 21, 2018. Answers (1)
- Explain the term fractional crystallization(Solved)
Explain the term fractional crystallization.
Date posted: April 21, 2018. Answers (1)
- Describe the process of extraction of Aluminium by electrolysis(Solved)
Describe the process of extraction of Aluminium by electrolysis.
Date posted: April 20, 2018. Answers (1)
- State uses of radio isotopes in the following: 1. Medicine 2. Agriculture 3. Industries(Solved)
State uses of radio isotopes in the following:
1. Medicine
2. Agriculture
3. Industries
Date posted: April 19, 2018. Answers (1)
- Given the following reagents describe how to prepare lead (ii) sulphate, Solid potassium sulphate, solid lead (ii) carbonate, dilute nitric (iv) acid and distilled water.(Solved)
Given the following reagents describe how to prepare lead (ii) sulphate: Solid potassium sulphate, solid lead (ii) carbonate, dilute nitric (iv) acid and distilled water.
Date posted: April 19, 2018. Answers (1)
- What are the advantages of universal indicators over other acid-base indicators?(Solved)
What are the advantages of universal indicators over other acid-base indicators?
Date posted: April 19, 2018. Answers (1)
- The heat of fusion and vaporization of water are 334.4Kj and 1159.4 Kj respectively. Explain why there is a big difference between the two
(Solved)
The heat of fusion and vaporization of water are 334.4Kj and 1159.4 Kj respectively. Explain why there is a big difference between the two
Date posted: April 18, 2018. Answers (1)
- A crystal of copper (II) sulphate was placed in a beaker of water. The beaker was left standing for two days without shaking. State and...(Solved)
A crystal of copper (II) sulphate was placed in a beaker of water. The beaker was left standing for two days without shaking. State and explain the observations that were made.
Date posted: April 17, 2018. Answers (1)
- Explain how the hotness of a bunsen burner flame can be increased(Solved)
Explain how the hotness of a bunsen burner flame can be increased.
Date posted: April 17, 2018. Answers (1)
- Explain why it is not advisable to store a solution of cadmium nitrate in a container made of zinc(Solved)
Explain why it is not advisable to store a solution of cadmium nitrate in a container made of zinc.
Date posted: April 17, 2018. Answers (1)
- Name two non-crystalline form of Sulphur(Solved)
Name two non-crystalline form of Sulphur.
Date posted: April 17, 2018. Answers (1)
- Dry ammonia gas is passed over heated lead(II) oxide in a combustion tube.
a) What observation would be made in the combustion tube
b) Outline a chemical...(Solved)
Dry ammonia gas is passed over heated lead(II) oxide in a combustion tube.
a) What observation would be made in the combustion tube
b) Outline a chemical test you would use to identify the colourless liquid collected in the u-tube
c) Name the colourless liquid
d) Write an equation for the reaction between ammonia and lead(II)oxide
Date posted: April 17, 2018. Answers (1)
- Name the method that can be used to obtain pure iron (III) chloride from a mixture of iron (III) chloride and sodium chloride(Solved)
Name the method that can be used to obtain pure iron (III) chloride from a mixture of iron (III) chloride and sodium chloride.
Date posted: April 14, 2018. Answers (1)
- What is a Neutrino? (Solved)
What is a Neutrino?
Date posted: April 14, 2018. Answers (1)
- State four applications of Nuclear Radiation(Solved)
State four applications of Nuclear Radiation.
Date posted: April 14, 2018. Answers (1)
- State and explain the five main components of Nuclear Power Plants that enables them use heat from nuclear reactors to produce electrical energy. (Solved)
State and explain the five main components of Nuclear Power Plants that enables them use heat from nuclear reactors to produce electrical energy.
Date posted: April 14, 2018. Answers (1)
- Give a reason why electrons are removed from the 4s orbital first then the d orbital to form cations(Solved)
Give a reason why electrons are removed from the 4s orbital first then the d orbital to form cations.
Date posted: April 14, 2018. Answers (1)
- State the four quantum numbers (Solved)
State the four quantum numbers.
Date posted: April 14, 2018. Answers (1)
- State the Heisenberg Uncertainty Principle (Solved)
State the Heisenberg Uncertainty Principle.
Date posted: April 14, 2018. Answers (1)