Almost all metals combine with oxygen to form metal oxides. Metal oxides are generally basic in nature. But some metal oxides show both basic as well as acidic behaviour. Different metals show different reactivities towards oxygen. Some react vigorously while some do not react at all.

(a) What happens when copper is heated in air ? (Give the equation of the reaction involved).

(b) Why are some metal oxides categorized as amphoteric ? Give one example.

(c) Complete the following equations :

(i) Na₂O(s) + H₂O(l) ⟶

(ii) Al₂O₃ + 2NaOH ⟶

OR

(c) On burning Sulphur in oxygen a colourless gas is produced.

(i) Write chemical equation for the reaction.

(ii) Name the gas formed.

(iii) State the nature of the gas.

(iv) What will be the action of this on a dry litmus paper ?

In order to trace the inheritance of traits Mendel crossed pea plants having one contrasting character or a pair of contrasting characters. When he crossed pea plants having round and yellow seeds with pea plants having wrinkled and green seeds, he observed that no plants with wrinkled and green seeds were obtained in the F₁ generation. When the F₁ generation pea plants were cross-bred by self-pollination, the F₂ generation had seeds with different combinations of shape and colour also.

(a) Write any two pairs of contrasting characteristics of pea plant used by Mendel other than those mentioned above.

(b) Differentiate between dominant and recessive traits.

(c) State the ratio of the combinations observed in the seeds of F₂ generation (in the above case). What do you interpret from this result ?

OR

(c) Given below is a cross between a pure violet flowered pea plant (V) and a pure white flowered pea plant (v). Diagrammatically explain what type of progeny is obtained in F₁ generation and F₂ generation :

Pure violet flowered plant (VV) x Pure white flowered plant (vv)