Question

Assertion : In a pressure cooker the water is brought to boil. The cooker is then removed from the stove. Now on removing the lid of the pressure cooker, the water starts boiling again.
Reason : The impurities in water bring down its boiling point.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (C)

The pressure cooker works on the principle that boiling point of a liquid increases with increase of vapour pressure above the liquid. Water, along with food to be cooked are heated in a closed vessel, so that the confined water vapour raises the superincumbent pressure. As a result, water boils at a temperature higher than $100^{\circ} C$. When the cooker is removed from the stove and the lid is removed, pressure again decreases due to which its boiling point decreases and water starts boiling again.