Give reasons: (a) Platinum, gold and silver are used to make jewellery. (b) Sodium, potassium and lithium are stored under oil. (c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking. (d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
These metals are unreactive (low in reactivity series), do not corrode easily, and retain their shiny, lustrous appearance. Their malleability and ductility allow crafting into intricate designs.
These alkali metals are highly reactive and react vigorously with air and moisture. Sodium and potassium can catch fire if kept in open. Oil prevents contact with air and water.
Aluminium forms a protective oxide layer on its surface when exposed to air, making it resistant to further corrosion. It is also lightweight, a good conductor of heat, and has high melting point.
It is easier to reduce metal oxides to pure metals than to reduce carbonates or sulphides directly. Roasting converts sulphides to oxides; calcination converts carbonates to oxides.
Explanation
(a) Section 3.4.1 explains that metals at the bottom of the activity series are least reactive. (b) Section 3.2.1 explains that sodium and potassium react so vigorously that they are kept immersed in kerosene oil. (c) Section 3.2.1 discusses the protective oxide layer and anodising process for aluminium. (d) Section 3.4.4 explains that it is easier to obtain metals from oxides compared to sulphides and carbonates.