The Novolac polymer has mass of $$963$$ g. The number of monomer units present in it are ______

Novolac is a linear polymer formed by the acid-catalysed condensation of phenol with formaldehyde, in which phenol rings are linked by methylene ($$-CH_2-$$) bridges. The repeating monomer unit thus has the structure $$HO-C_6H_4-CH_2-$$ and a molecular formula of $$C_7H_7O$$.

To determine its molecular weight, note that $$M = 7 \times 12 + 7 \times 1 + 1 \times 16 = 84 + 7 + 16 = 107 \text{ g/mol}$$.

Substituting this value into the expression for the number of units, $$n = \frac{\text{Mass of polymer}}{\text{Mass of one monomer unit}} = \frac{963}{107} = 9$$. Therefore, the Novolac polymer contains 9 monomer units.