a) They have delocalized valency electrons
b) Aluminium has three delocalized electrons hence better conductor than magnesium which has two
- It is resistant to corrosion unlike magnesium
johnmulu answered the question on February 21, 2017 at 07:49
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When the oxide of element H was heated with element H was heated with powdered carbon the mixture glowed and carbon (IV) oxide was formed. When the experiment was repeated using the oxide of element J, there was no apparent reaction.
(Solved)
When the oxide of element H was heated with element H was heated with powdered carbon the mixture glowed and carbon (IV) oxide was formed. When the experiment was repeated using the oxide of element J, there was no apparent reaction.
a) Suggest one method that can be used to extract element J from its oxide
b) Arrange the elements H, J and carbon in the order of their decreasing reactivity.
Date posted:
February 21, 2017
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Answers (1)
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Aluminium metal is a good conductor and is used for overhead cables. State any other two properties that make aluminium suitable for this use.
(Solved)
Aluminium metal is a good conductor and is used for overhead cables. State any other two properties that make aluminium suitable for this use.
Date posted:
February 21, 2017
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Answers (1)
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State one advantage and one disadvantage of using petrol containing tetraethyl lead in motor vehicles
(Solved)
Give one advantage and one disadvantage of using petrol containing tetraethyl lead in motor vehicles
Date posted:
February 21, 2017
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Answers (1)
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Explain why it is not advisable to use wood ash for cleaning aluminium utensils
and state the advantage of using duralumin in place of aluminium for manufacture of aeroplane n parts
(Solved)
a) Explain why it is not advisable to use wood ash for cleaning aluminium utensils
b) Duralumin is an alloy of aluminium. What is the advantage of using duralumin in place of aluminium for manufacture of aeroplane parts
Date posted:
February 21, 2017
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Answers (1)
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A student electroplated a spoon with copper metal. Write an equation for the process that took place at the cathode.
(Solved)
A student electroplated a spoon with copper metal. Write an equation for the process that took place at the cathode.
Date posted:
February 18, 2017
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Answers (1)
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Hydrogen and oxygen can be obtained by electrolysis of acidified water. Using equations for the reactions at the electrodes, explain why the volume of hydrogen obtained is twice that of oxygen.
(Solved)
Hydrogen and oxygen can be obtained by electrolysis of acidified water. Using equations for the reactions at the electrodes, explain why the volume of hydrogen obtained is twice that of oxygen.
Date posted:
February 18, 2017
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Answers (1)
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During the electrolysis of aqueous silver nitrate, a current of 5.0 A was passed through the electrolyte for 3 hours.
(Solved)
During the electrolysis of aqueous silver nitrate, a current of 5.0 A was passed through the electrolyte for 3 hours.
a) Write the equation for the reaction which took place at the anode
b) Calculate the mass of silver deposited. (Ag = 108; IF = 96500 C)
Date posted:
February 16, 2017
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Answers (1)
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When brine is electrolysed using inert electrodes, chlorine gas is liberated at the anode instead of oxygen. Explain this observation and name the product formed at the cathode.
(Solved)
a) When brine is electrolysed using inert electrodes, chlorine gas is liberated at the anode instead of oxygen. Explain this observation.
b) Name the product formed at the cathode.
Date posted:
February 16, 2017
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Answers (1)
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During purification of copper by electrolysis, 1.48 g of copper were deposited when current was passed through aqueous copper (II) sulphate for 2$\frac{1}{2}$ hours. Calculate the amount of current used. (Cu = 63.5; 1 F = 96500 C
(Solved)
During purification of copper by electrolysis, 1.48 g of copper were deposited when current was passed through aqueous copper (II) sulphate for 2$\frac{1}{2}$ hours. Calculate the amount of current used. (Cu = 63.5; 1 F = 96500 C).
Date posted:
February 16, 2017
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Answers (1)
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An element P has a relative atomic mass of 88. When a current of 0.5 amperes was passed through the fused chloride of P for 32 minutes and 10 seconds, 0.44 g of P were deposited at the cathode.
(Solved)
An element P has a relative atomic mass of 88. When a current of 0.5 amperes was passed through the fused chloride of P for 32 minutes and 10 seconds, 0.44 g of P were deposited at the cathode. Determine the charge on an ion of P.
(1 Faraday = 96500 Coulombs)
Date posted:
February 16, 2017
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Answers (1)
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Give reason why aluminium metal would protect iron from rusting better than zinc metal
(Solved)
Give reason why aluminium metal would protect iron from rusting better than zinc metal.
Date posted:
February 16, 2017
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Answers (1)
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Aqueous potassium sulphate was electrolyzed using platinum electrodes in a cell......
(Solved)
Aqueous potassium sulphate was electrolyzed using platinum electrodes in a cell.
a) Name the products formed at the cathode and anode
b) How does the concentration of the electrolyte change during electrolysis?
c) Why would it not be advisable to electrolyse aqueous potassium sulphate using potassium metal electrodes?
Date posted:
February 16, 2017
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Answers (1)
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State and explain how the rate of reaction between zinc granules and steam can be increased
(Solved)
State and explain how the rate of reaction between zinc granules and steam can be increased.
Date posted:
February 15, 2017
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Answers (1)
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State the Hess's Law and its applications
(Solved)
State the Hess's Law and its applications.
Hess's law States that if a chemical change can be made to take place in two or more steps, the amount of the total heat change is the same no matter which method is used.
Its applications are:
1.Determination of heat of formation of substances which cannot be measured experimentally. Substances like methane,carbon dioxide and benzene cannot be prepared by uniting there elements. Therefore it is not possible to measure the heat of formation of certain compound directly.
2.Determination of heat of transition. The heat of transition from one allotropic form to another can also be calculated with the help of Hess's law.
3.Determination of heat of various reaction. By using Hess's law we can calculate enthalpies of many reactions which can not be measured directly. For example the enthalpy of dimerization of nitrogen dioxide.
Date posted:
February 15, 2017
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Answers (1)
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State two factors that should be considered when choosing fuel for cooking
(Solved)
State two factors that should be considered when choosing fuel for cooking.
Date posted:
February 15, 2017
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Answers (1)
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When pure water is heated at 1 atmospheric pressure at sea level, the temperature of the water does not rise beyond 100oC
(Solved)
When pure water is heated at 1 atmospheric pressure at sea level, the temperature of the water does not rise beyond 100oC, even with continued heating. Explain this observation
Date posted:
February 15, 2017
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Answers (1)
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Explain why the enthalapy of neutralization of ethanoic acid with sodium hydroxide is different from that of hydrochloric acid with sodium hydroxide
(Solved)
Explain why the enthalapy of neutralization of ethanoic acid with sodium hydroxide is different from that of hydrochloric acid with sodium hydroxide.
Date posted:
February 15, 2017
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Answers (1)
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When magnesium burns in air, it forms a white solid and a grey-green solid. When a few drops of water are added to the mixture, a gas that turns red litmus paper blue is evolved. Identify the:
(Solved)
When magnesium burns in air, it forms a white solid and a grey-green solid. When a few drops of water are added to the mixture, a gas that turns red litmus paper blue is evolved.
Identify the:
i) White solid
ii) Gas evolved and the gas
I) Name of gas
II) Use of the gas.
Date posted:
February 15, 2017
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Answers (1)
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Naturally occurring magnesium consists of three isotopes. 78.6%24Mg; 10%25Mg and 26Mg. Calculate to one decimal place, the relative atomic mass of magnesium
(Solved)
Naturally occurring magnesium consists of three isotopes. 78.6%24Mg; 10%25Mg and 26Mg. Calculate to one decimal place, the relative atomic mass of magnesium.
Date posted:
February 15, 2017
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Answers (1)
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Describe how sodium carbonate is used to remove water hardness.
(Solved)
Describe how sodium carbonate is used to remove water hardness.
Date posted:
February 15, 2017
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Answers (1)