What is the chemical formula of rust?

Iqbal treated a lustrous,divalent element $M$ with sodium hydroxide. He observed the formation of bubbles in the reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both the reactions.

Bronze is an alloy of:

Which of the following ores is in the form of sulphide?

What type of oxides are formed when non-metal elements combine with dioxygen gas?

$A$ mixture of equal amounts of $H_2$ and $Cl_2$ gases in a gas jar produces white fumes in the absence of sunlight. What are these white fumes?