[ch101em]

I don't understand how to do these questions or what the question is asking.  Could you provide some key steps to solving this?

The radius of an argon atom is 4.2*10^-8 cm.  What percent of the total volume of a 1 mole sample of argon gas at STP is occupied by Argon atoms?

a. 5
b. 10
c. 0.83
d. 0.0008
e. 2

One mole of Xenon atoms occupy 0.90 percent of the total gas sample at STP.  What is the radius of Xenon?

a. 2.0*10^-8 cm
b. 4.0*10^-9 cm
c. 1.0*10^-7 cm
d. 5.0*10^-12 cm
e. 4.3*10^-8 cm

Thanks

[sdekivit]

use simple maths to answer these questions (hint: consider the atoms like spheres)

[ch101em]

use simple maths to answer these questions (hint: consider the atoms like spheres)

I understand that part, but the part that I don't understand is the question.  what does it mean by what percent of Argon gas is occupied by argon atoms.

And, what does it mean by .90 percent of gas sample is argon.

[sjb]

I understand that part, but the part that I don't understand is the question.  what does it mean by what percent of Argon gas is occupied by argon atoms.

And, what does it mean by .90 percent of gas sample is argon.

At least in terms of these questions, you need to appreciate that between the atoms of a pure gas is nothing, nada, zip (to a good approximation). Tough concept, I know, took me a while to think that way.

Pointers towards (2)

You know (or can look up) the molar volume of an ideal gas at STP, so 0.90% of this is a set volume. As there are an Avogadro's number of atoms in this sample, a single atom will have a set volume, then from considering the atom as a sphere you can calculate its radius.

Question 1 is essentially the same, but in reverse. From the radius of one atom you can calculate atomic volume, then molar volume and compare that to the total volume of space taken up.


S

[ch101em]

Oh, I get what it means now, thanks.