(a) What are amphoteric oxides? Give two examples. (b) Metals such as Sodium and Potassium are kept immersed is Kerosene, why? (c) Give the balanced chemical equation for the reaction between Aluminium and steam. (d) Name a non metal:      (i) Which is a liquid at room temperature?      (ii) Which is lustrous? Or (a) What are the main two allotropes of carbon? Distinguish these two allotropes on the basis of hardness and electrical conduction. (b) Why Aluminium articles have a longer life and attractive finish compared to many other metals? (c) Explain the following terms:     (i) Ore     (ii) Gangue (d) What is common feature in the electronic configuration of metal atom?

Asked by Topperlearning User | 24th Jul, 2017, 01:50: PM

Expert Answer:

(a)Amphoteric oxides are those oxides which show properties of both acids as well as bases to form salts and water. Ex: Aluminium oxide(Al2O3) and ZnO are examples of amphoteric oxides. (b) Metals such as Sodium and Potassium are kept immersed is Kerosene because they are very reactive and have high affinity towards oxygen and will violently react with atmospheric oxygen on contact with air. (c) Aluminium reacts readily with steam to give aluminium oxide and hydrogen gas. The reaction does not always occur. This is due to a thin but strong layer of aluminium oxide being coated onto the metal, thus preventing it from the reaction. Aluminium + Steam → Aluminium oxide + Hydrogen 2Al(s) + 3H2O(g) → Al2O3(s) + 3H2(g) (d) (i) Non-metal which is a liquid at room temperature - Bromine      (ii) Non-metal which is lustrous - Iodine                                                             OR (a)Diamond and graphite are the two allotropes of carbon. Diamond - (i) hardest substance (ii) electrical insulator Graphite - (i) comparatively soft, it is slippery over layers (ii) good electrical conductor (b)Aluminium articles have a longer life and attractive finish compared to many other metals because of the formation of a thin transparent protective film cover of Aluminium oxide on the surface of Al formed due to its spontaneous reaction with oxygen. (c) (i) Ore : An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element(s). (ii) Gangue: In mining,earthly impurities including silica, mud etc. associated with the ore are called gangue.   (d) Electronic configuration of metal atom tells us about the type of  bond the metal will be forming. For example: In the formation of calcium chloride, chlorine only needs one electron to complete its octet so two atoms of chlorine accept one electron each lost by calcium atom.

Aswered by  | 24th Jul, 2017, 03:50: PM