Chemistry moles question

if the molar volume is 24dm3:
a)what is the mass of 1dm3 of oxygen (o2)
b) what is the volume of 10g of helium?

revising chemistry and not understanding moles :(

Remember these equations:
Moles = Mass/Molecular Mass

Moles = Volume you have been given / 24dm^3

So for question a)

We need the mass of O2, well if we work out the moles first we can do it:

Moles = 1 / 24
Moles = 0.04167.

Then use moles = mass/mr
mass = moles x mr
mass = 0.04167 x (16 x 2) (One oxygen atom has a mass of 16, two have a mass of 32)
mass = 1.33g

b) Volume of 10g of helium? First get it into moles!

Moles = mass/mr
Moles = 10/4
Moles = 2.5

Then we use Moles = Volume/24dm^3
Volume = Moles x 24
Volume = 2.5 x 24
Volume = 60dm^3

Hope I've helped! If you remember those equations, you can do those questions easy!

you must know that a mole is just a certain number of units (6.02E23 units)
and
a mole is equal to the gram formula mass of a unit
so
a molar volume of 24 dm^3 translates to
24 dm^3 / mol or inversely as 1 mol / 24 dm^3

a)
1 dm^3 * 1 mol / 24 dm^3 = 1/24 mol = 0.0417 mol

b)
10 g He * 1 mol / 4 g He * 24 dm^3 / mol = 60 dm^3