Explain step by step: What is the laboratory preparation of carbon iv oxide

1. Reactants:

• Calcium carbonate ($\ce{CaCO3}$): Usually in the form of marble chips.
• Dilute hydrochloric acid ($\ce{HCl}$): Other dilute acids like sulfuric acid can be used, but hydrochloric acid is preferred as calcium sulfate formed with sulfuric acid is sparingly soluble and can coat the marble chips, stopping the reaction.

2. Chemical Equation:
The reaction produces calcium chloride, water, and carbon dioxide gas:

$$\ce{CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + H2O(l) + CO2(g)}$$

3. Apparatus Setup:

• A conical flask or Woulfe's bottle is used as the reaction vessel.
• A thistle funnel is inserted through a rubber stopper into the flask for adding the acid. The end of the thistle funnel must be submerged below the acid level to prevent gas from escaping through it.
• A delivery tube is also inserted through the stopper to channel the produced gas.
• The gas is collected in a gas jar.

4. Procedure:

• Place a quantity of marble chips ($\ce{CaCO3}$) into the conical flask.
• Pour dilute hydrochloric acid through the thistle funnel into the flask, ensuring the funnel's stem is below the acid surface.
• The reaction will start immediately, producing effervescence (bubbles of $\ce{CO2}$ gas).

5. Collection Method:

• Carbon dioxide is denser than air (molar mass of $\ce{CO2}$ is approximately $44 \text{ g/mol}$, while the average molar mass of air is about $29 \text{ g/mol}$).
• Therefore, it is collected by the downward displacement of air in a gas jar. The delivery tube is placed at the bottom of the gas jar, and the heavier $\ce{CO2}$ fills the jar from the bottom up, pushing the lighter air out.
• It can also be collected over water, but since $\ce{CO2}$ is sparingly soluble in water, collection by downward displacement of air is more common, especially if dry gas is required.

6. Purification and Drying (Optional):

• To remove any acid spray, the gas can be passed through a wash bottle containing water.
• To dry the gas, it can be passed through a drying tower containing anhydrous calcium chloride or a wash bottle containing concentrated sulfuric acid ($\ce{H2SO4}$).