when a piece of limestone reacts with dilute HCl. a gas X is produced, when gas X is passed through lime water. A white precipitate Y is fanned. On passing excess of gas X, the white precipitate dissolves, forming a soluble compound Z, X, Y and Z, respectively, are:

Correct option is C

CO₂, CaCO₃, Ca(OH)₂

• CO₂: This is the gas produced when limestone reacts with dilute HCl, as expected.
• CaCO₃: This is the white precipitate formed when CO₂ is passed through lime water.
• Ca(OH)₂: This is lime water, which is a solution of calcium hydroxide.
  

• CO₂: Again, this is the gas produced during the reaction between limestone and HCl.
• CaCO₂: This compound doesn’t exist. The correct compound is calcium carbonate (CaCO₃), which is the white precipitate formed in lime water.
• CaO: This is calcium oxide, also known as quicklime.

CO₂, Ca(HCO₃)₂, CaCO₃

• CO₂: This is correct as the gas produced during the reaction with HCl.
• Ca(HCO₃)₂: This is calcium bicarbonate.
• CaCO₃: This is the white precipitate that forms when CO₂ is bubbled through lime water, but the reaction with excess CO₂ leads to the dissolution of this precipitate,.