Question

Is Boric Acid a protic acid? Explain.

Answer 1

According to Arrhenius, protic acid is that acid which donates proton. In other words, an acid that releases ${H^ + }$ also called oxonium ions $\left( {{H_3}{O^ + }} \right)$ aqueous known as protic acid. Examples are ${H_2}S{O_4}$, HCl, ${H_2}S{O_4}$ etc.

Complete answer:

According to Arrhenius an acid is that substance which when added to water then there will be an increase of hydrogen ion or oxonium ion concentration and decrease of hydroxide concentration. Similarly, according to Arrhenius a base is that substance which when added to water then there will be an increase of hydroxide ion concentration and decrement in hydrogen or oxonium concentration or oxonium ion concentration.
Boron is a typical non-metal, belonging to group 13. Orthoboric acid, ${H_3}B{O_3}$ is a white crystalline solid, with soapy touch. It is slightly soluble in water but highly soluble in hot water. Orthoboric acid is prepared by acidifying an aqueous solution of borax. It is planar in structure in which there are various layers of $B{O_3}$. Boric acid is a weak monobasic acid. Because it is not able to release ${H^ + }$ions on its own. It receives $O{H^ - }$ ions from water molecules to complete its octet and in turn releases ${H^ + }$ ions.
${\rm{B(OH}}{{\rm{)}}_3}{\rm{ + 2HOH }} \to {\rm{ B(OH)}}_4^ - \, + \,{H_3}{O^ + }$
It does not contain hydrogen ions so not a protonic acid but they can accept electrons from $O{H^ - }$ so it is a Lewis acid.

So, we can say that Boric acid is not a protic acid.

Note: Orthoboric acid on heating above 370K forms metaboric acid, $HB{O_{2\,}}$ which on further heating yields boric oxide, ${B_2}{O_3}$. Boric acid has many uses like it can be used as an antiseptic, medical dressings etc. It has many antibacterial properties. It is also very poisonous.