MediumChemistryHigh School (9–10)GeneralCarbon and Its Compounds › Reactions and Uses of Carbon CompoundsConceptualBoard Exam
Two colourless liquids are in unlabelled bottles…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two colourless liquids are in unlabelled bottles. One is ethanol, and the other is ethanoic acid. Describe two simple tests that tell them apart, and what you would see.
Need a reminder? The key ideaShow
Ethanol, , gives hydrogen with sodium, and ethene with hot concentrated sulphuric acid. Ethanoic acid, , is a weak acid: it turns blue litmus red and fizzes with carbonates. Acid + alcohol, with a few drops of concentrated sulphuric acid, gives an ester and water.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Litmus. Ethanoic acid turns blue litmus red. Ethanol leaves it blue.
Step 2. Sodium hydrogencarbonate. Ethanoic acid fizzes and gives carbon dioxide, which turns lime water milky. Ethanol does nothing.
Step 3. Smell, with care. Ethanoic acid smells of vinegar.
Answer: litmus and sodium hydrogencarbonate both pick out the acid.
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