Molar Mass of unknown gas

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In summary, to determine the molar mass of an unknown gas, you can use the ideal gas law to calculate the volume of the vessel at a certain temperature and pressure, then use that volume to determine the number of moles of the unknown gas. From there, you can calculate the molecular weight of the unknown gas.
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1. A sample bulb contained 0.712 g H2 (g) at a certain temperature and pressure. Under the same conditions of temperature and pressure, the bulb can hold 13.0 g of an unknown gas. What is the molar mass of the unknown gas?

Obtaining H2 volume from the ideal gas law (assuming STP) and then using that volume to obtain the unknown gas density (with STP) is the correct way to obtain the molar mass?

I would appreciate some help

Thank you.
 
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Assume the gas follows the ideal gas law. For the hydrogen example you know the pressure/temperature and the number of moles. From that you can calculate the volume of the vessel. Use this solution (same pressure, temperature and volume) to determine the number of moles of the unknown gas. From that you can calculate the molecular weight of the unknown gas.
 
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I would approach this problem by first determining the number of moles of H2 present in the sample bulb using the ideal gas law (PV = nRT). From there, I would use the given mass (0.712 g) and molar mass (2 g/mol) of H2 to calculate the volume of H2 present in the sample bulb.

Next, I would use the ideal gas law again to calculate the volume of the unknown gas that would occupy 0.712 g of H2 at the same temperature and pressure. This would give me the volume of the unknown gas in the sample bulb.

Then, I would use the given mass (13.0 g) and the calculated volume to find the density of the unknown gas. From there, I could use the density to calculate the molar mass of the unknown gas using the formula M = mRT/PV.

It is important to note that this method assumes that the unknown gas behaves as an ideal gas, which may not always be the case. Additional experiments or data may be needed to confirm this assumption and obtain a more accurate molar mass.
 

1. What is the definition of molar mass?

Molar mass is the mass of one mole of a substance, measured in grams per mole (g/mol).

2. How is the molar mass of a gas determined?

The molar mass of a gas can be determined by measuring its density, temperature, and pressure and using the ideal gas law equation (PV = nRT) to calculate the number of moles. The molar mass can then be found by dividing the mass of the gas by the number of moles.

3. Why is it important to know the molar mass of a gas?

The molar mass of a gas is important because it helps to determine the identity of the gas, as different gases have different molar masses. It is also necessary for calculating the amount of gas present in a given volume.

4. Can the molar mass of a gas change?

No, the molar mass of a gas is a constant value for a specific gas at a given temperature and pressure. However, the molar mass of a gas can vary depending on the temperature and pressure at which it is measured.

5. How does the molar mass of a gas affect its behavior?

The molar mass of a gas affects its behavior in terms of its density and diffusion rate. Heavier gases with higher molar masses will have a higher density and will diffuse more slowly compared to lighter gases with lower molar masses.

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