Which substance is used for the chemical reduction of metal oxides like chromium and manganese to obtain the metal?

Which type of oxide is $CO_{2}$?

Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.

Which of the following statements is incorrect?

What happens when:
$(i)$ $A$ piece of calcium is dropped in water.
$(ii)$ Sodium is kept exposed in air.
$(iii)$ Iron nail is dipped in copper sulphate solution.
$(iv)$ Potassium is dropped in cold water.
$(v)$ Carbon dioxide is compressed in water at high pressure.
Give chemical equations involved in all the above reactions and balance them.

Name one metal and one non-metal that are found in a liquid state at room temperature.