Part A: You are in a mountain range with atmospheric air pressure of 520 mmHg an
ID: 971364 • Letter: P
Question
Part A: You are in a mountain range with atmospheric air pressure of 520 mmHg and you wish to boil some eggs. What is the approximate boiling point of the water at this air pressure? Express the temp. In degrees Celsius using two significant figures.Part C: A sealed glass jar has a small amount of water on the bottom. The rest of the volume in the jar is taken up by helium gas at a partial pressure of 526 mmHg, and water vapor. If the total pressure inside the jar is 760. mmHg, what is the temp. of the water? Express the temp. numerically in degrees Celsuis.
Explanation / Answer
PartA:
The standard boiling point for water at 100°C is for standard atmospheric pressure, 760 mmHg. It is the experience of high altitude hikers that it takes longer to cook food at altitude because the boiling point of water is lower. On the other hand, food cooks more quickly in a pressure cooker because the boiling point is elevated. Raising or lowering the pressure by about 28 mmHg will change the boiling point by 1°C.
(760-520)/28 = 8.57oC
100 - 8.57 oC = 91.4oC
PartB:
Clausius clapeyron equation:
ln(P1/P2) = (Hvap / R) x (1/T2 - 1/T1)
where.
P1 =760mmHg - 526mmHg = 234mmHg
P2 = 760mmHg
Hvap = 40.68 kJ/mole = 40680 J/mole (same ref as above)
R = 8.314 J/moleK
T2 = 100°C = 373.15K
T1 = ?
ln(234/760) = ((40680 J/mole) / (8.314 J/moleK)) x (1/ 373.15 - 1/T1)
1/T1 = 0.002921
T1 = 342.4K = 69.2°C