Q. (a) A student took sulphur powder on a spatula and heated it. Then he collected the gas evolved by inverting a test tube over it. Write a balanced chemical equation for the reaction taking place. What will be the action of this gas on :
Ans: (i) dry litmus paper and (ii) moist litmus paper.
(i) Gas is SO2, no reaction with dry litmus paper.
(ii) Bleaches moist litmus paper or turn blue litmus paper red.
(iii) S (s)1O2(g) ------------> SO2(g)
Q. What is Thermit reaction? Mention its application.
Ans: Reaction between ferric oxide and aluminium produce iron and release high amount of heat. This reaction is called thermit reaction.
Q. (a) How do we find whether a given element is a non metal, if we know its electronic configuration? (b) With the help of a reaction show that zinc is more reactive than iron. (c) In nature aluminium is found in combined state whereas silver is found in Free State. Give reason. (d) Why should we not throw small pieces of sodium into a sink in the laboratory? (e) Name any two amphoteric oxides.
Ans: (a) Elements with 4 - 8 valence electrons
(b) Zn(s)1FeSO4(aq) ------- > ZnSO4(aq)1Fe(s)
Green white Zn displaces Fe from its salt solution, the colour of solution changes.
(c) Aluminium is reactive while silver is uncreative or a noble metal.
(d) Sodium is highly reactive and can cause explosion or accident when it reacts with water in sink, and atmospheric air.
(e) Zinc oxide and aluminium oxide ( or any other)