Question

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

Answer 1

Correct Answer: 9

To determine the number of monomer units in a Novolac polymer with a mass of 963 g, follow these steps:

1. Identify the monomer unit of Novolac: Novolac is a phenol-formaldehyde resin formed primarily from phenol (C₆H₅OH) and formaldehyde (CH₂O).
2. Determine the molar mass of the monomer unit: For simplification, consider the repeating unit as C₇H₆O (approximation involving phenol and formaldehyde). Thus, the molar mass M is calculated as:
   M = (7 × 12.01 g/mol) + (6 × 1.01 g/mol) + (1 × 16.00 g/mol) = 106.12 g/mol.
3. Calculate the number of moles of the polymer using its total mass: Number of moles n is given by:
   n = \(\frac{\text{Mass of polymer (g)}}{\text{Molar mass of monomer (g/mol)}}\) = \(\frac{963 \text{ g}}{106.12 \text{ g/mol}}\approx 9.08 \text{ moles}\).
4. Confirm this value of 9.08 is within the provided range of 9,9, verifying the result is valid within expected precision constraints.

Thus, the number of monomer units in the Novolac polymer is approximately 9, fitting well within the given range.