CBSE Class 10 Science 2021 Term 1 Solved Paper

Question : 38

Total: 60

Observe the diagram of an activity given below. What does it help to conclude, when the person exhales into the test-tube?

Percentage of carbon dioxide is more in inhaled air.
Fermentation occurs in the presence of oxygen.
Percentage of carbon dioxide is more in the exhaled air.
Fermentation occurs in the presence of carbon dioxide.

Solution:

Carbon dioxide gas turns lime water milky. When air is blown from the mouth into a test-tube containing lime water, the lime water turns milky because the air we breathe out has more percentage of CO2 gas. The lime water turns milky due to the formation of calcium carbonate when carbon dioxide combines with calcium hydroxide (limewater).

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