A 0.500 g sample of a polysaccharide is completely hydrolysed with acid to give 0.00012 mol of glucose. Calculate the average degree of polymerisation (DP) of the polysaccharide.
Answer
DP ≈ 23
The correct answer is DP ≈ 23 — Thus the average number of glucose units linked in the polymer is about 23.
Step-by-step solution
- Calculate the mass of glucose produced: mass = moles × molar mass of glucose (180 g mol⁻¹).
- mass of glucose = 0.00012 mol × 180 g mol⁻¹ = 0.0216 g.
- Degree of polymerisation = mass of polysaccharide ÷ mass of one glucose unit.
- DP = 0.500 g ÷ 0.0216 g ≈ 23.1, which is reported as 23.
- Thus the average number of glucose units linked in the polymer is about 23.
Common mistake: Using the number of moles directly instead of converting to mass of a glucose unit.
Concept tested: Degree of polymerisation
Published · How this solution was prepared and checked
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