(a) Explain the following.

      (i) Roasting
      (ii) Calcination.

(b) What are amphoteric oxides? Write the name of such one oxide.

(c) By which two metals is brass alloy formed?

(a) 

(i) Roasting is the process in which the ore is heated below its melting point in presence of air to oxidise the impurities. eg: carbon, sulphur, etc removed as their gaseous oxides.

(ii) Calcination is the process of heating the ore below its melting point absence of air to remove volatile impurities like arsenic etc. 

(b) In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid as well as a base. Many metals (such as copper, zinc, tin, lead, aluminum, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide.

(c) Brass is a metal alloy made of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.