Property-prediction exam problem clinic
≈ 48 minProperty-prediction exam problem clinic
To compare physical properties, first decide what is being compared: boiling point, melting point, vapour pressure, viscosity or solubility. Then identify the particles and relevant forces. Molecules of similar mass can have different boiling points if one has an O-H, N-H or F-H group that enables hydrogen bonding. Larger electron clouds can strengthen London dispersion forces, but branching, shape and polarity can complicate comparisons. Use relative language such as higher, lower, stronger or weaker, and make your claim conditional on the molecules and conditions in the question.
Work it through
Ethanol and dimethyl ether have the same formula, C₂H₆O, but ethanol contains an O-H group and can form hydrogen bonds between molecules. Dimethyl ether cannot hydrogen bond to itself in the same way. Therefore ethanol has stronger intermolecular attractions and a higher boiling point. The formula alone is not enough; you need the structural arrangement.
Mastery target
Compare two molecular substances by naming the decisive structural feature, the relevant intermolecular force and the predicted relative property.
Why does ethanol generally boil at a higher temperature than dimethyl ether, although both have formula C₂H₆O?
Name the key chemistry term from Property-prediction exam problem clinic that best fits the explanation and visual model.
What is the most defensible first step when comparing boiling points of two molecular substances?
Which statement corrects a common misunderstanding in Property-prediction exam problem clinic?