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

💡 Solution & Explanation

**Step 1: Identify the monomer unit** Novolac is a phenol-formaldehyde polymer. The repeating unit has the molecular formula C₇H₆O (phenol minus one H, plus formaldehyde unit). **Step 2: Calculate molar mass of the monomer unit** Molar mass = (7 × 12) + (6 × 1) + (1 × 16) = 84 + 6 + 16 = 106 g/mol **Step 3: Calculate moles of monomer units** Using the formula: Number of moles = Mass ÷ Molar mass Moles = 963 g ÷ 106 g/mol = 9.09 mol ≈ 9 mol **Step 4: Convert moles to number of monomer units** Number of units = Moles × Avogadro's number = 9 × 6.022 × 10²³ However, if the question asks for the number of monomer *units* in terms of the repeating formula units (not individual molecules), we use the mole value directly. **Step 5: Final answer** The number of monomer units = 9 Therefore, the answer is 9.