“Boiling Point Concept: The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure.
Effect of Altitude: At higher altitudes (e.g., mountains), the atmospheric pressure is lower compared to sea level.
Since the external pressure is less, water molecules require less energy to escape into vapor → so water boils at a lower temperature.
Assertion Check: (A) is true because the boiling point of water decreases with increasing altitude.
Reason Check: (R) is false because atmospheric pressure actually decreases with altitude, not increases.
Example: Pressure at sea level = 1 atm, at Mount Everest summit ≈ 0.33 atm.
Conclusion:
Since (A) is true and (R) is false, the correct answer is (a).”