Question

II Revi Part A The vapor pressure of a substance describes how readily molecules at the surface of the substance enter the gaseous phase. At the boiling point of a liquid, the liquid's vapor pressure is equal to or greater than the atmospheric pressure exerted on the surface of the liquid. Since the atmospheric pressure at higher elevations is lower than at sea level, the boiling point of water decreases as the elevation increases. The atmospheric pressure at sea level is 760 mm Hg. This pressure decreases by 19.8 mm Hg for every 1000-ft increase in elevation. What is the boiling point of water at an elevation of 1.55x104 ft ? Express your answer with the appropriate units using three significant figures. ► View Available Hint(s) ? Elevation Pressure 760 o ft mmHg 1000 ft 740.2 mmHg T: MÅ T= Value R o 2 Units T = Submit Previous Answers 2000 ft 720.4 mmHg X Incorrect; Try Again; 5 attempts remaining The boiling point of water decreases 0.05°C for every 1 mmHg drop in atmospheric pressure.

Answer 1

According to the problem;

This pressure decreases by 19.8 mm Hg for every 1000- ft increase in elevation.

Total pressure drop at 1.55*10^4:

19. 8 mm Hg / 1000 ft * 1.55 x10^4 ft = 306.9 mm Hg

The boiling point of water decreases 0.05 C for every 1 mm Hg drop in atmospheric pressure.

Total temperature drop = 0.05 deg C / 1 mm Hg * 306.9 mm Hg = 15.345 deg C

Boiling point = 100 – 15.345 = 84.655 deg C