At a height of 310 km above the Earth\'s surface, an astronaut finds that the at

Question

At a height of 310 km above the Earth's surface, an astronaut finds that the atmospheric pressure is about 1.27E-8 mmHg and the temperature is 597 K. How many molecules of gas are there per milliliter at this altitude? (Enter the number of molecules, with no units.)

Two gases, argon (30.6 grams) and carbon monoxide (8.8 grams), are confined in a container at a pressure of 960.0 torr. Calculate the partial pressure of argon in torr. (You may need to look up the formula for one or both of your gases.)

Liquid helium at 4.2 K has a density of 0.147 g/mL. Suppose that a 2.00-L metal bottle that contains air at 108K and 3.0 atm pressure is sealed off. If we inject 90.0 mL of liquid helium and allow the entire system to warm to room temperature (25

Explanation / Answer

for 3rd one

110ml He x 0.147g/ml = 16.17g He
16.17g He / 4g/mole = 4.04moles

moles air = pv/rt
moles air = 2.5atm x 1L / (0.0821L-atm/mole-K x 95K) = 0.32moles air present
if we warm the air alone, p1/t1 = p2/t2
2.5atm / 95K = xatm / 298K
7.84atm air pressure

injecting 4.04moles He into 1L flask at 95K
p = nrt/v = 4.04moles x 0.0821L-atm/mole-K x 95K / 1L = 31.5atm
pHe: p1/t1 = p2/t2
31.5atm /95K = p2 / 298K, p2 = 98.84atm

total pressure at 298K = 106.68atm
or
the total pressure at 95 of air and He = 34atm (31.5atm from above for He)
p1/t1 = p2/t2
34atm / 95K = xatm / 298K
total pressure = 106.65atm

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