When the gas evolved during thermal decomposition of calcium carbonate is passed through lime water, it turns milky. Which gas does this confirm?
Answer and explanation
Correct answer: Carbon dioxide
Thermal decomposition of calcium carbonate produces carbon dioxide: \(\mathrm{CaCO_3 \xrightarrow{\Delta} CaO + CO_2}\). When this gas is passed through lime water, \(\mathrm{Ca(OH)_2}\), it forms an insoluble precipitate of calcium carbonate, making the lime water milky: \(\mathrm{Ca(OH)_2 + CO_2 \rightarrow CaCO_3 \downarrow + H_2O}\). Oxygen does not form a calcium carbonate precipitate under these conditions.
Frequently asked questions
What is the correct answer to this question?
Carbon dioxide
Why is this the correct answer?
Thermal decomposition of calcium carbonate produces carbon dioxide: \(\mathrm{CaCO_3 \xrightarrow{\Delta} CaO + CO_2}\). When this gas is passed through lime water, \(\mathrm{Ca(OH)_2}\), it forms an insoluble precipitate of calcium carbonate, making the lime water milky: \(\mathrm{Ca(OH)_2 + CO_2 \rightarrow CaCO_3 \downarrow + H_2O}\). Oxygen does not form a calcium carbonate precipitate under these conditions.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
