(a) Anirudh took two metal oxides; aluminium oxide and magnesium oxide as shown in the pictures given below. But he forgot to label them. How will you guide/ help Anirudh to identify the oxides and label them?

(b) In an activity Aishu was given two substances; Copper Sulphide (Cu₂S) and Copper Oxide (Cu₂O) to obtain copper from these compounds. She was able to extract Copper successfully. Illustrate with the help of chemical equations how Aishu might have completed the activity.

(a) Anirudh can prepare aqueous solutions of both oxides. (MgO forms a mildly basic solution; Al₂O₃ is insoluble.) Dip red litmus into each sample.
The solution that turns red litmus to blue is Magnesium oxide (MgO) and the solution with which red litmus does not show any colour change is Aluminium oxide (Al₂O₃).

(b) When copper sulphide is heated in air, it undergoes roasting, reacting with oxygen to form copper oxide (Cu₂O) and sulphur dioxide gas then, the freshly formed copper oxide reacts further with more copper sulphide, producing copper metal and sulphur dioxide gas again.

Hence, copper is obtained in the metallic form — by roasting and reduction as shown below :

2Cu₂S(s) + 3O₂(g) $\xrightarrow{\text {Heat}}$ 2Cu₂O(s) + 2SO₂(g)

2Cu₂O(s) + Cu₂S(s) $\xrightarrow{\text {Heat}}$ 6Cu(s) + SO₂(g)