What type of oxides are formed when non-metals combine with oxygen?

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 here.

(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.

State two ways to prevent the rusting of iron.

Give reasons:

(a) Platinum, gold and silver are used to make jewellery

(b) Sodium, potassium and lithium are stored under oil.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.