By which method/process is sulphur obtained from the earth's crust?

Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?
$(i)$ $Au$
$(ii)$ $Cu$
$(iii)$ $Na$
$(iv)$ $K$

Why can oxides of highly reactive metals not be reduced by carbon?

$A$ metal $E$ is stored under kerosene oil. When a small piece of it is left open in the air,it catches fire. When the product formed is dissolved in water,it turns red litmus blue.
$(i)$ Name the metal $E$.
$(ii)$ Write the chemical equations for the reaction when it is exposed to air and when the product is dissolved in water.
$(iii)$ Explain the process by which the metal is obtained from its molten chloride.

What is the chemical formula of nitric acid?

When sulfur dioxide gas is passed through lime water,which insoluble substance is formed that turns the solution milky?