Solved 2023 Question Paper CBSE Class 10 Science — Question 1
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In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the solution 'X' the solution 'X' first turn milky and then colourless.
The option that justifies the above stated observation is that 'X' is aqueous calcium hydroxide and
it turns milky due to carbon dioxide gas liberated in the reaction and after sometime it becomes colourless due to formation of calcium carbonate.
it turns milky due to formation of calcium carbonate and on passing excess of carbon dioxide it becomes colourless due to formation of calcium hydrogen carbonate which is soluble in water.
it turns milky due to passing of carbon dioxide through it. It turns colourless as on further passing carbon dioxide, sodium hydrogen carbonate is formed which is soluble in water.
the carbon dioxide liberated during the reaction turns lime water milky due to formation of calcium hydrogen carbonate and after some time it turns colourless due to formation of calcium carbonate which is soluble in water.
it turns milky due to formation of calcium carbonate and on passing excess of carbon dioxide it becomes colourless due to formation of calcium hydrogen carbonate which is soluble in water.
Reason — The reaction between sodium carbonate and HCl gas produces carbon dioxide gas.
Na2CO3 + 2HCl (dil.) ⟶ 2NaCl + H2O + CO2
Solution X is aq. calcium hydroxide which reacts with carbon dioxide gas and forms calcium carbonate, which turns the solution milky.
Ca(OH)2 + CO2 ⟶ CaCO3 + H2O
However, on passing excess carbon dioxide, the calcium hydrogen carbonate is formed, which is soluble in water and hence, the solution X becomes colourless.
CaCO3 + H2O + CO2 ⟶ Ca(HCO3)2