Apentix/AP Chemistry/Unit 3: Intermolecular Forces and Properties/Question
AP Chemistrymediummcq1 pt

At room temperature, glycerol pours sluggishly while ethanol flows freely. Both are small alcohols. The dominant reason for the difference is that glycerol:

A.carries three O-H groups per molecule, forming a much denser hydrogen-bonding network that resists flow
B.is nonpolar, so its molecules mechanically interlock
C.has the lower molar mass, so its molecules collide more often
D.contains dissolved ionic impurities that thicken it

Explanation

Core Concept

Viscosity measures how strongly a liquid resists internal flow, and hydrogen bonds are the strongest attractions available between these neutral molecules. Ethanol offers one hydroxyl group per molecule, whereas glycerol offers three, so each glycerol molecule donates and accepts many more hydrogen bonds simultaneously. The resulting three-dimensional network entangles neighbors, so layers drag against one another and pour slowly. Molar mass and size differences are secondary to this multiplicity of bonding sites.

Correct Answer

Acarries three O-H groups per molecule, forming a much denser hydrogen-bonding network that resists flow

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