The number of hydroxyl Groups is 3.
The reaction of an alcohol with "CH"_3"COCl" is
"RO-H" + "CH"_3"CO-Cl" → "RO-COCH"_3 + "HCl"
Assume that the compound "X" has a molecular mass of x " u".
For each "OH" group that reacts, "X" loses 1 " H" atom (1.008 u) to form an "RO" group.
The mass of the "RO" group is (x –1.008)" u".
The "RO" group then adds a "CH"_3"CO" unit (43.04 u).
So the mass of the product is (x -1.008 + 43.04)" u" = (x+ 42.03)" u
"X" gains 42.03 u of mass for every OH group that reacts.
So "42.03 u gained" = "1 OH group".
We can create a conversion factor by dividing each side of the equation by "42.03 u gained":
"1 OH group"/"42.03 u gained" = 1.
Then
126 cancel("u gained") × "1 OH group"/(42.03 cancel("u gained")) = "3.00 OH groups" ≈ "3 OH groups".
The compound contains 3 OH groups.
