Food cans are coated with tin and not with zinc because-

(a) How could you use them to distinguish between samples of metals and non-metals?

(b) Access the usefulness of these tests in distinguishing between metals and non-metals.

Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in the figure below.
  
(a) What will be the action of gas on

(i) Dry litmus paper?

(ii) Moist litmus paper?

(b) Write a balanced chemical equation for the reaction taking place.