Question

Water cycle is the real life example of a double decomposition reaction. State true or false.

Answer 1

Hint: Water cycle is a complete natural cycle and decomposition reaction occurs between two reacting molecules. Water gets regenerated after a complete cycle and in double decomposition no such regeneration is there.

Complete answer:
Water cycle is a cycle that includes movement of water above the surface of the earth and below the surface. There are various water bodies in the earth such as fresh water, river water, ice and saline water. The water continuously evaporates from the surface and then condenses or reaches back to earth in the form of rain. So the continuous movement of water occurs. It is purely natural phenomena and does involve physical changes, states of matter (solid, liquid and gas) interchange.
On the other hand in double decomposition reactions there is a chemical reaction that occurs between two compounds. In this the two constituent reactants interchange their positive and negative ions to each other. For example AB and CD are the two reactants then double decomposition reaction occurs as follow:
${\text{AB + CD = AD + CB}}$
In Double displacement reaction the anion of the two reactants gets interchanged to each other that is why it is called double displacement reaction.
We can clearly see, there is no relationship between water cycle and double displacement or double decomposition reaction hence the given statement is wrong

So the statement is false.

Note: Let us look at some of the examples of double decomposition reaction:
${\text{Ca(OH}}{{\text{)}}_{\text{2}}}{\text{ + 2N}}{{\text{H}}_{\text{4}}}{\text{Cl }} \to {\text{CaC}}{{\text{l}}_{\text{2}}}{\text{ + 2N}}{{\text{H}}_{\text{4}}}{\text{OH}}$
${\text{AgN}}{{\text{O}}_{\text{3}}}{\text{ + KCl}} \to {\text{AgCl + KN}}{{\text{O}}_{\text{3}}}$
These reactions are also known as exchange reactions. Neutralization reactions are good example of double decomposition reactions.