In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.
Step 1: Understand the experiment:
The experiment involves passing two types of air through lime water (Ca(OH)₂) in separate test tubes:
- Diagram (I): Atmospheric air
- Diagram (II): Exhaled air
Step 2: Composition of the air samples:
- Atmospheric air contains only about 0.03–0.04% CO₂.
- Exhaled air from human lungs contains a much higher concentration of CO₂, about 4%.
Step 3: Reaction with lime water:
Both samples are passed through lime water. The carbon dioxide in the air reacts with calcium hydroxide (lime water) to form calcium carbonate, which causes the solution to turn milky:
\[
\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}
\]
- This reaction forms insoluble calcium carbonate (CaCO₃), which appears as milkiness.
Step 4: Observations:
- In test tube (I), since atmospheric air has less CO₂, the milkiness develops slowly.
- In test tube (II), exhaled air has more CO₂, so the lime water turns milky much faster.
Step 5: Conclusion:
The faster appearance of milkiness in test tube (II) shows that exhaled air contains more carbon dioxide than atmospheric air. Hence, the rate of reaction with lime water is higher.
