Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologyeasymcq1 pt

Ethanol mixes with water in any proportion, while ethane of similar size barely dissolves. Which comparison explains this contrast?

A.The hydroxyl group of ethanol is polar and forms hydrogen bonds with water, while ethane offers only nonpolar C-H bonds
B.The carbon-carbon bond of ethane is ionic, so water pulls the molecule apart
C.Ethanol's extra oxygen doubles its mass, and heavier molecules dissolve more easily
D.Ethane's hydrogens carry partial positive charges that repel the positive side of water

Explanation

Core Concept

Dissolving requires favorable interactions between solute and solvent. Replacing one hydrogen of ethane with a hydroxyl group creates a strongly polar O-H bond: the oxygen attracts water molecules and the hydrogen donates hydrogen bonds to them. These attractions repay the energy cost of mixing. Ethane presents only nearly nonpolar C-H and C-C bonds, so water gains no favorable contacts by surrounding it, and the hydrophobic effect keeps it out.

Correct Answer

AThe hydroxyl group of ethanol is polar and forms hydrogen bonds with water, while ethane offers only nonpolar C-H bonds

More Unit 1: Chemistry of Life practice questions

Try a random question →

Practice more AP Biology questions with full explanations

Practice Unit 1: Chemistry of Life Questions →