Question

Which is stronger acid in the following pair? 3-Chlorophenol and 2-Ethylphenol.

Answer 1

Negative inductive effect can be shown by the halogen, when the halogens get attached with the alkyl group, they tend to induce the $- I$ effect or negative induction, while creating $+ I$ effect or positive induction, on the alkyl group. On the contrary alkyl group generates $+ I$ or positive induction effect.

Complete step by step answer
“Acids are those substances which tend to lose protons that are ${H^ + }$ ions”. Whoever tends to lose ${H^ + }$ ions faster is the strongest acid.
If any substance get attached with halogen, halogen tries to pull electron from that substance and creates negative inductive effects this negative inductive effect creates ${\delta ^ + }$ on the substance and ${\delta ^ - }$ on that halogen. On the other hand, if any substance gets attached with an alkyl group, the alkyl group tries to donate electrons to that substance and creates a positive inductive effect. This positive inductive effect creates a ${\delta ^ - }$ on the substance and ${\delta ^ + }$ on that alkyl group.
When halogen is attached to acid it pulls the electron density from the alkyl or aryl group, making itself ${\delta ^ - }$, therefore alkyl or aryl group gets electron deficit and pulls the electron from oxygen of hydroxide group, resulting in the oxygen to get less electronegative, which in turn pulls the electron from hydrogen resulting in the release of ${H^ + }$ ion.
When alkyl group is attached to acid it donates the electron density from the alkyl or aryl group, making itself ${\delta ^ + }$ , therefore alkyl or aryl group gets electron rich and donates the electron to oxygen of hydroxide group, resulting in the oxygen to get more electronegative, this electronegative oxygen will not loss ${H^ + }$ ion that easily.
Therefore, 3-chlorophenol is a stronger acid than 2-ethylphenol.

Note
If there is an inductive effect by the attaching of an electronegative element on the molecule then you should consider that greater the number of the electronegative element more the polarizing power of that molecule. Opposite is applicable when we attach an electropositive element.