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Question : 25
Total: 30
Write balanced chemical equations to explain what happens, when
(i) Mercuric oxide is heated.
(ii) Mixture of cuprous oxide and cuprous sulphide is heated.
(iii) Aluminium is reacted with manganese dioxide.
(iv) Ferric oxide is reduced with aluminium.
(v) Zinc carbonate undergoes calcination. OR
(i) By the transfer of electrons, illustrate the formation of bond in magnesium chloride and identify the ions present in this compound.
(ii) Ionic compounds are solids. Give reasons.
(iii) With the help of a labelled diagram show the experimental set up of action of steam on a metal.
(i) Mercuric oxide is heated.
(ii) Mixture of cuprous oxide and cuprous sulphide is heated.
(iii) Aluminium is reacted with manganese dioxide.
(iv) Ferric oxide is reduced with aluminium.
(v) Zinc carbonate undergoes calcination. OR
(i) By the transfer of electrons, illustrate the formation of bond in magnesium chloride and identify the ions present in this compound.
(ii) Ionic compounds are solids. Give reasons.
(iii) With the help of a labelled diagram show the experimental set up of action of steam on a metal.
Solution:
(i) Cinnabar ( HgS ) ( HgO )
2 HgO ( s )
2 Hg ( l ) + O 2 ( g )
(ii) When a mixture of copper oxide and copper sulphide is heated metallic copper is formed along with the evolution of the sulphur dioxide gas. The reaction equation is as follows.
2 Cu 2 O + Cu 2 S → 6 Cu + SO 2
(iii) When aluminium powder is reacted with manganese dioxide, Manganese along with the aluminium oxide is formed with the evolution of heat and the following reaction takes place:
3 MnO 2 ( s ) + 4 Al ( s ) → 3 Mn ( l ) + 2 Al 2 O 3 ( s ) + Heat
(iv) When ferric oxide is reduced with aluminium a displacement reaction takes place and this reaction is highly exothermic. The amount of heat evolved is so large that the metals are produced in the molten state. In fact, the reaction of iron (III) oxide ( Fe 2 O 3 )
Fe 2 O 3 ( s ) + 2 Al ( s ) → 2 Fe ( l ) + Al 2 O 3 ( s ) + Heat
(v) The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination. The chemical reaction that takes place during calcination of zinc ores can be shown as follows:
Mg 2 + Cl −
(ii) Ionic compounds are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and break into pieces when pressure is applied.
(ii) When a mixture of copper oxide and copper sulphide is heated metallic copper is formed along with the evolution of the sulphur dioxide gas. The reaction equation is as follows.
(iii) When aluminium powder is reacted with manganese dioxide, Manganese along with the aluminium oxide is formed with the evolution of heat and the following reaction takes place:
Ions present in this compound are
(ii) Ionic compounds are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and break into pieces when pressure is applied.
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