Typical molecular-weight scale for polymers: select the most appropriate order-of-magnitude range for number-average molecular weights observed in commercial polymers.

Introduction / Context:
Polymeric materials derive their properties from very high molecular weights compared to small molecules. Understanding the typical range helps interpret viscosity, mechanical strength, and processing behavior.

Given Data / Assumptions:

• We refer to number-average (Mn) or weight-average (Mw) molecular weights for common commercial polymers.
• Extremes may exist, but typical commercial ranges are needed.

Concept / Approach:
Commodity and engineering polymers generally span from a few hundred (oligomers/prepolymers) up to several million g/mol. Values above 10^7 g/mol are uncommon in standard processing due to extreme viscosity and limited melt flow. Therefore, 10^2–10^7 captures the practical landscape.

Step-by-Step Solution:
Compare each range with known polymer data (e.g., PE, PS, PVC, PET).Select the broad but realistic 10^2–10^7 range.Exclude unrealistically high bands for routine processing.

Verification / Alternative check:
Gel-permeation chromatography data for commercial resins commonly report Mw in the 10^4–10^6 range.

Why Other Options Are Wrong:
10–10^3 is too low for typical high-molecular-weight resins.10^7–10^9 and higher are extraordinary and not standard for melt processing.

Common Pitfalls:
Confusing degree of polymerisation (DP) with molecular weight units; DP times repeat-unit mass gives MW.

Final Answer:
10^2 to 10^7