A student dropped few pieces of marble in dilute hydrochloric acid, contained in a test tube. The evolved gas was then passed through lime water. 

What change would be observed in lime water ? What will happen if excess of gas is passed through lime water ?

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1 Answers

CaCO3 + zHcl→ CaCl2 + H2O + CO2

Marble is calcium carbonate and on reacting with HCI releases CO2.

Ca(OH)2 +CO2→CaCO3+H2O

.Ca(OH)2 -Lime water

CaCO-White ppt

Lime water turns milky due to the formation of white precipitate of CaCO3. On passing excess CO2, milkIness disappears because Ca(HCO3)2 is formed which is soluble in water.

CaCO3+H2O+CO2→ Ca(HCO3) 

 Ca(HCO3)- Soluble in water

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