Which of the following pairs will give displacement reactions ?

In the electrolytic refining of a metal $M$, what would you take as the anode, the cathode and the electrolyte ?

Give reasons : Sodium, potassium and lithium are stored under oil.

Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below.

$(a)$ What will be the action of gas on

$(i)$ dry litmus paper ?

$(ii)$ moist litmus paper ?

$(b)$ Write a balanced chemical equation for the reaction taking place.

Metallic oxides of zinc, magnesium and copper were heated with the following metals.

In which cases will you find displacement reactions taking place ?

An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be