Gasoline and motor oil are chemically similar. They are both mixtures of nonpolar hydrocarbons containing carbon and hydrogen atoms. However, motor oil is much more viscous than gasoline. Which substance probably has the higher average molar mass?

Motor oil probably has the higher average molar mass. Its hydrocarbon molecules are generally larger than those in gasoline, with more carbon and hydrogen atoms per molecule. Larger molecules tend to have stronger attractions between them, which contributes to motor oil’s greater viscosity.

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