"$A$ solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed".
$(i)$ Translate the above statement into a chemical equation.

State what happens when:
$(a)$ Chlorine gas is passed through dry slaked lime.
Also write the chemical equation in each case.

Write true or false for the following statement: On heating the crystals of ferrous sulphate,the colour changes from green to grey.

Give a reason why:
$(i)$ Why is a decomposition reaction called the opposite of a combination reaction?

What is rancidity? Mention any two ways by which rancidity can be prevented?

$A$ silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
$(a)$ Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
$(b)$ Name the black substance formed and give its chemical formula.