A student took a lime solution and passed a gas 'A' through it. The solution becomes turgid. This
solution was divided into two parts. In the first part, more of gas 'A' was passed. In the second part
concentrated sulphuric acid was added. A white precipitate was formed in second part.
(a) The gas mentioned in above passage is
(i) 02
(ii) H2
iii) CO2
(iv) H2S
(b) Does the final product formed in second case contain water of crystallisation? Yes/No
(c) Write the chemical equation for the process in which gas 'A' was evolved.
(d) What happened when more of gas 'A' was passed through the turgid solution? Give chemical
equation.
Answers
a. The Gas A which reacts with the lime solution to turn the lime water milky is carbon dioxide (CO2). The reaction takes place as follows:
Ca(OH)2 + CO2 → CaCO3 + H2O
The lime solution turns milky due to the formation of calcium carbonate.
b. Water of crystallization is formed when calcium carbonate is formed.
c. A chemical reaction which yields CO2 is the breakdown of carbonic acid as follows:
H2CO3 → H2O + CO2
d. when more of gas 'A' was passed through the turgid solution, the calcium carbonate that was formed initially dissolves because of the formation a soluble salt compound, i.e., calcium hydrogen carbonate. As a result, the solution turns clear. The following chemical reaction occurs:
CaCO3 + CO2 + H2O → Ca(HCO3)2
Answer:
Same as given above
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