Question

How would you show that exhaled air has more carbon dioxide than inhaled air

Answer 1

Your friend has answered correctly- the exhaled air contains carbon dioxide-this can be easily proved with the help of lime water. Take two beakers- A & B containing lime water in equal quantity. Now leave the beaker A undisturbed and  blow air in the beaker B with the help of straw. It will be clearly observed that lime water in beaker B first turns milky due to high concentration of CO2  where as  lime water in beaker A turns milk after taking some time due to low concentation of CO2 in the atmosphere.

Answer 2

Carbon dioxide turns lime water milky. Based on this principle, experiment can be designed to show that exhaled air has more carbon dioxide than inhaled air.

1 Take two test tubes half filled with lime water.

2 With the help of glass tubes, clips and stoppers having two holes, set up an apparatus as shown below:

3 The middle rubber tube is used to breath in and out through the mouth.

4 Suck air through the rubber tube and open clip X and close clip Y. The inhaled air passes through the lime water present in test tube A. Now, exhale through the tube again and close clip X and open clip Y. The exhaled air passes through the lime water in test tube B.

5 The lime water in test tube B turns milky. This shows that exhaled air has more carbon dioxide.