CH-528
Separation and purification
Chemistry · Secondary 3 · Hard · Separation and purification
A student heats a mixture of ethanol (b.p. 78 °C) and water (b.p. 100 °C) in a distillation set‑up. The thermometer reading rises and stays constant at 78 °C for some time before increasing again. Which statement explains this observation?
- Ethanol is decomposing at 78 °C, so the temperature cannot change.
- The thermometer is faulty and stuck at 78 °C.
- Ethanol is boiling at 78 °C, so the temperature stays constant while it changes to gas.
- Water is boiling at 78 °C, so the temperature stays constant until all water boils.
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