Which catalyst is used in the industrial manufacture of hydrogen gas?

The electrical conductivity and melting point of an alloy is:

Write the balanced chemical equation for the reaction of aluminium when heated in air. Also,write the name of the product.

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.

Which of the following methods is used for the concentration of ore?

In the electrolytic refining of copper metal,what is used as the cathode?