In a blast furnace,what prevents the oxidation of molten iron?

Give reasons for the following:
$(i)$ Alloys are used in electrical heating devices rather than pure metals.
$(ii)$ Gold ornaments look new even after several years of use.
$(iii)$ An iron grill should be painted frequently.

An alloy is

Describe ionic compounds on the basis of the following properties:
$(i)$ Strong force of attraction between positive and negative ions:
$(ii)$ Solubility of compounds in water.
$(iii)$ Electrical conductivity.

Which of the following metals is the most reactive?

Which ore is concentrated by the froth flotation process?