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WAChemistryQuick questions
Unit 4: Organic Chemistry and Chemical Synthesis
Quick questions on Physical properties and intermolecular forces of organic compounds: WACE Year 12 Chemistry
2short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are boiling point trends across families?Show answer
For molecules of comparable carbon number, the boiling point order reflects the strongest force present. Carboxylic acids and alcohols (hydrogen bonding) boil highest; aldehydes and ketones (dipole-dipole) are intermediate; alkanes (dispersion only) boil lowest. Carboxylic acids boil even higher than alcohols of similar size because they can form two hydrogen bonds, dimerising in the pure liquid.
What is water solubility?Show answer
A molecule is water-soluble if it can form favourable interactions (especially hydrogen bonds) with water. Small alcohols, carboxylic acids and amines are very soluble because their polar group hydrogen bonds with water. As the non-polar carbon chain grows, it dominates and solubility falls: methanol and ethanol mix freely with water, but longer-chain alcohols become increasingly insoluble. Alkanes are essentially insoluble because they are non-polar.
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