An unknown substance dissolves in water to give a basic solution and gives a gas with acid that turns lime water milky. Which substance could it be?
Answer and explanation
Correct answer: Sodium carbonate
A gas that turns lime water milky is carbon dioxide, so the unknown substance should contain a carbonate or hydrogencarbonate ion. Sodium carbonate reacts with an acid to release CO2 and forms a basic aqueous solution because carbonate ions hydrolyse water to produce hydroxide ions. Sodium chloride is nearly neutral, ammonium chloride is acidic, and copper sulfate is not the expected carbonate source. Hence option A is correct.
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What is the correct answer to this question?
Sodium carbonate
Why is this the correct answer?
A gas that turns lime water milky is carbon dioxide, so the unknown substance should contain a carbonate or hydrogencarbonate ion. Sodium carbonate reacts with an acid to release CO2 and forms a basic aqueous solution because carbonate ions hydrolyse water to produce hydroxide ions. Sodium chloride is nearly neutral, ammonium chloride is acidic, and copper sulfate is not the expected carbonate source. Hence option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
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