What are the constituents of a solder alloy? Which property of solder makes it suitable for welding electrical wires?

A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.

The following reaction takes place when aluminium powder is heated with MnO₂

(a) Is aluminium getting reduced?

(b) Is MnO₂ getting oxidised?

A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with HCl and NaOH.

A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved.