Question

The number of hydroxyl group(s) in Q is ?

Answer 1

Hint :This step is the multiple reaction in which the intermediate product is formed. The final product of the reaction is phyrophosperic acid. Phyrophosperic acid molecular structure is $H_4{O}_7{P}_2$

Complete Step By Step Answer:
The first step is the acid catalyzed dehydration reaction in which the alcoholic group is converted to an alkene group. A dehydration reaction is a reaction in which an organic compound undergoes loss of water molecules to form an alkene group with a carbon-carbon double bond. The primary carbocation form is the carbon group with a positive ion charge. The secondary carbocation rearranges itself into tertiary carbocation to form a more stable alkene group.
In the next step dihydroxylation reaction takes place in which an alkene group is converted into a vicinal diol in presence of excess potassium permanganate $KMn{O}_4$ . It is done by oxidation of transition metal. The metal acts as a catalyst to complete the reaction and double bond is hydrolyzed attaching the $4-OH$ groups to the compound.
Pyrophosphoric acid is also known as diphosphoric acid. It is a colorless, odorless, hygroscopic and is soluble compound in water, diethyl ether, and ethyl alcohol.

As stated in the reaction that $4-OH$ groups are being attached. The total number of hydroxyl groups in pyrophosphoric acid is $4$ .
Therefore, the number of hydroxyl group(s) in Q is $4$

Note :
Anions, salts, and esters of pyrophosphoric acid are known as pyrophosphates. It is an acyclic phosphorus acid anhydride obtained by condensation of two molecules of phosphoric acid.