chem ideal gas law problem? im stuck?

Question

This uses the ideal gas law:
An elemental gas has a mass of 10.3 g. If the volume is 58.4 L and the pressure is 0.997368 atm at 275.5 K, what is the gas?

Answer 1

What we have to know in order to identify the gas is its molecular mass. This can be calculated from the usual Gas Law:

PV = nRT.

Let´s see how:

1) m = 10.3 g, V = 58.4 L, P = 0.9997 atm, T = 275.5 K

With the given units, the constant R has a value of:

R = 0.0872 atm L / K mol

2) You know that:

n=m/M ......where: n=number of moles, m=mass, M=molecular weight

3) You can substitute in Gas Law:

PV = (m/M)RT

we solve for M:

M = mRT / PV

4) we substitute the given values above:

M = (10.3 g)(0.0872 atm L / K mol)(275.5K) / (0.997368 atm)(58.4 L)

M = 4.24 g/mol

The only gas that can give this molecular weight could be:

Helium

that has a molecular weight of 4.007 g/mol


Hope it helps you.

Good luck!

Answer 2

Using pV = nRT will give you n, as long as you convert all the quantities correctly, and use the correct value of R. Molar mass = mass/n, and you should then be able to identify the gas.

Answer 3

It seems that the pressure, temperature and voulme are "Standard" find a gas that has a molcular weight of 10.3.

Answer 4

PV = mRT/M
where M is the molecular weigth (MW) of the gas.
You have V, P, R (look in the book), T and m.
Calculate M and look what gas has this MW