What is the percentage concentration of sodium hydroxide solution used in the Bayer process (in $\%$)?

Which of the following metals exists in nature in liquid state?

$A$ metal $M$ forms an oxide having the formula $M_{2}O_{3}$. It dissolves in both dilute sulphuric acid and dilute sodium hydroxide solution. Identify the metal and write the chemical equations for the reactions involved.

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.

By which method is the concentration of sulphide ore carried out?

$(i)$ Define the term 'anode mud'. Name the electrode made of pure metal.
$(ii)$ Give the reactions taking place at cathode and at anode during the electrolytic refining of copper.