Question

1. If a sample of nitrogen gas is collected over water at 70°C has a total pressure of 2590 mm Hg,

what would be the pressure of the nitrogen alone?
Vapor pressure of water at 70'C = 233.7 mm Hg
2. Find the total pressure for a mixture that contains four gases with partial pressures of 5.00 atm,
4.65 atm, 3.01 atm, and 121.56 kPa.
3. A flask contains a mixture of the three following gases: 1 mol N₂ at 460 mm Hg, 1 mol Ne at 275
mm Hg, and 1 mol O₂ at 520 mm Hg. What is the total pressure in the flask?
4. A mixture of helium and neon gases is collected over water at 28.0 C and 745 mmHg. If the
partial pressure of helium is 368 mmHg, what is the partial pressure of neon? The vapor pressure
of water at 28 °C is 28.3 mm Hg.
5. A mixture of three gases, oxygen, nitrogen, and helium, is at a total pressure of 6.11 atm. The
partial pressure of the oxygen is 1780 mmHg, the nitrogen is at 174.1 kPa, and the partial
pressure of the helium is unknown. What is the partial pressure of helium in atm?
Oxygen gas was collected over water at a barometric pressure of 732.0 mmHg and 23 °C. What is
the partial pressure of the oxygen? The vapor pressure of water at 23°C = 21.1 mm Hg.

Answer 1

Explanation: To find the pressure of the nitrogen alone, we need to subtract the vapor pressure of water at 70°C from the total pressure. Therefore, the pressure of nitrogen alone would be:

2590 mm Hg - 233.7 mm Hg = 2356.3 mm Hg

To find the total pressure of the mixture, we simply add the partial pressures of the individual gases:

Total pressure = 5.00 atm + 4.65 atm + 3.01 atm + 121.56 kPa

= 12.53 atm

Note that we need to convert the partial pressure of the fourth gas from kPa to atm before adding it to the other partial pressures.

The total pressure in the flask is the sum of the partial pressures of each gas:

Total pressure = 460 mm Hg + 275 mm Hg + 520 mm Hg

= 1255 mm Hg

To find the partial pressure of neon, we need to subtract the vapor pressure of water at 28.0°C from the total pressure, and then subtract the partial pressure of helium from the result:

Partial pressure of neon = Total pressure - Vapor pressure of water - Partial pressure of helium

= 745 mmHg - 28.3 mmHg - 368 mmHg

= 348.7 mmHg

The partial pressure of helium can be found by subtracting the partial pressures of oxygen and nitrogen from the total pressure:

Partial pressure of helium = Total pressure - Partial pressure of oxygen - Partial pressure of nitrogen

= 6.11 atm - 1780 mmHg - 174.1 kPa

= 0.273 atm

Note that we need to convert the partial pressure of nitrogen from kPa to atm before subtracting it from the total pressure.

To find the partial pressure of oxygen, we need to subtract the vapor pressure of water at 23°C from the total pressure:

Partial pressure of oxygen = Total pressure - Vapor pressure of water

= 732.0 mmHg - 21.1 mmHg

= 710.9 mmHg