Question

Assertion (A): Benzene does not decolourize the $ B{r_2} $ water.
Reason (R): Benzene is stabilized by resonance due to delocalization of $\pi $ electrons.
(A) Both Assertion and Reason are true and Reason is the correct Explanation for Assertion.
(B) Both Assertion and Reason are true but Reason is not the correct Explanation for Assertion.
(C) Assertion is True but Reason is False.
(D) Assertion is False but Reason is true.

Answer 1

Hint: The bromine water test is used to detect the functional groups like alkanes or alkenes from the compound. The alkenes react with bromine water to give an additional reaction under dark conditions, bromine water decolorizes to confirm the presence of alkenes. Alkanes on the other hand do not react with the bromine water and the colour of bromine water does not change.

Complete answer:
Bromine water test also known as saturation test is used to test the compound if it is saturated or it is unsaturated.
Benzene does not react with bromine, benzene is an aromatic compound even if it contains unsaturated double bonds. This double bond is delocalized so benzene is a stable compound. It does not give an additional reaction bromine water test because it wants to maintain its stability.
Benzene shows resonance, benzene does not have alternate double bonds in resonance it has single $\pi $ bond, this $\pi $ bond is formed by the interaction of p-orbitals with each carbon atom present in the benzene this $\pi $ bond contains two $\pi $ electrons which are responsible for the stability of benzene because they are delocalize all over the benzene ring.

Additional Information:
Bromine water is also known as bromide bromate solution or bromine solution it is prepared in a chemical lab by reacting fumes of bromine with water but this method is not safe, a more suitable method to prepare bromine water is to react Sodium Bromide $ NaBr $ with Hydrochloric acid $ HCl $ .

Note:
Bromine water test is commonly used to test the presence of functional groups like Enols, Phenol, Glucose, Aldehyde. If any of these functional groups is detected an additional reaction takes place and bromine water decolorizes.