Help on Universal Gas?

Question

1. What pressure will 26g of helium exert when placed in a steel clinder at 200 degrees Celsius?
2. The vapour pressure of water at 21 degrees Celsius is 2.5kPa. Calculate the minimum volume occupied by 1g of water at this temperature?
3. What is the density of hydrogen at 200 degrees Celsius and 200kPa? (Assume a volume of 1L)

Answer 1

1. You need to know the volume of the container. Then, convert the mass of helium to moles by dividing by the atomic weight of He. Use the ideal gas law to calculate the pressure. Make sure you convert the temperature into Kelvin.

PV = nRT

2. Use the same equation. Again, you have to convert the mass of water into moles. Then, plug everything into the ideal gas law and calculate the volume. Make sure you use the correct units, and convert everything you need to before calculating with the ideal gas law.

3. Use the ideal gas law again to calculate the number of moles (You've got P, V and T, all you need is n). Now, convert the moles into a mass, and divide that by the volume to get g/L.