$A$ 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?

What happens when
$(a)$ $ZnCO_{3}$ is heated in the absence of oxygen?
$(b)$ $A$ mixture of $Cu_{2}O$ and $Cu_{2}S$ is heated?

During the refining of copper by electrolysis,copper deposits at the $....$.

State reasons for the following:
$(i)$ Metals are good conductors of heat.
$(ii)$ Addition of some silver to pure gold for making ornaments.
$(iii)$ Inability of non-metals to displace hydrogen from dilute sulphuric acid.

Which non-metal element exists in a liquid state at room temperature?

How many carats is pure gold?