Solve Gas Law: Volume at STP from Pressure & Temp of Hydrogen Gas

In summary, the volume of the collected hydrogen gas at STP can be determined using the ideal gas law equation PV=nRT, with standard pressure and temperature values of 760 mmHg and 273 Kelvin, respectively. However, the volume must be corrected for the presence of water vapor at 25°C, with a vapor pressure of 23.8 mmHg. Therefore, the pressure of the dry hydrogen gas in the collected sample must be calculated before finding the final volume at STP.
  • #1
lolphysics3
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Homework Statement


Hydrogen gas is collected over water at 25°C. The atmospheric pressure in the room is 745 mm Hg and the volume of gas in the container is 43.5mL. The vapor pressure of water at 25°C is 23.8 mm Hg. Determine the volume the gas would occupy at STP.


Homework Equations


PV=nRT
PV/NT=PV/NT
standard pressure=760 mm Hg or 1 atm
standard temperature= 273 Kelvin


The Attempt at a Solution


Well for this one I wasn't really sure if they just gave me excess information to throw me off. My first response was to say that the volume would just be 43.5mL. None of the equations provided above worked with just the information given. Is this really as easy at it seems?
 
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  • #2
No, it is not that easy, and there is no excess information.

First of all, you know the volume at 745 mmHg and 25°C, these are not STP conditions, so the answer can't be 43.5mL.

Then, some of the volume is taken by the water vapor, and you are asked about the volume of just hydrogen - so you have to take 23.8 mmHg into account. What is the pressure of the dry hydrogen in the collected sample?
 

FAQ: Solve Gas Law: Volume at STP from Pressure & Temp of Hydrogen Gas

1. What is the STP for hydrogen gas?

The STP (Standard Temperature and Pressure) for hydrogen gas is 0°C (273.15 K) and 1 atmosphere (atm) of pressure.

2. How do you calculate the volume of hydrogen gas at STP?

The volume of hydrogen gas at STP can be calculated using the ideal gas law, which is PV = nRT. In this equation, P represents pressure, V represents volume, n represents the number of moles of hydrogen gas, R represents the gas constant, and T represents temperature in Kelvin.

3. Can the ideal gas law be used for hydrogen gas at non-STP conditions?

Yes, the ideal gas law can be used for hydrogen gas at any conditions, as long as the temperature is in Kelvin and the pressure is in atm or another appropriate unit for the gas constant used.

4. What is the gas constant for hydrogen gas?

The gas constant for hydrogen gas is 8.314 J/mol·K. However, some sources use a different gas constant based on the units used for pressure and volume (for example, 0.0821 L·atm/mol·K or 62.36 L·mmHg/mol·K).

5. How does the volume of hydrogen gas at STP compare to its volume at other conditions?

At STP, the volume of hydrogen gas is 22.4 liters per mole. However, at other conditions, the volume will vary depending on the temperature and pressure. As temperature increases, the volume of hydrogen gas will also increase. As pressure increases, the volume of hydrogen gas will decrease.

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