Calculations using the Ideal Gas Law

[ArcHorizon]

Homework Statement:

I got this question from one of the tutors, and they told me that this was a basic question. To me, it seemed to be a hard question, since it was my first time taking lessons for Physics Class.
So, this is the question.

[An ideal monatomic gas is kept in a container of volume 2.1 × 10–4 m3, temperature 310 K and pressure 5.3 × 105 Pa.]
[The volume of the gas is increased to 6.8 × 10–4 m3 at a constant temperature.]

a.i) State what is meant by an ideal gas.
a.ii) Calculate the number of atoms in the gas.
a.iii) Calculate, in J, the internal energy of the gas.

Relevant Equations:

Not Sure This will help but
pV = nRT

Pressure in Pa
Volume in m^3
Temperature in kelvin
n is number of moles
R is gas constant

2.1 * 10^-4m/3 Temperature 310K
Pressure: 5.3 * 105 Pa
So the Ideal gas formula is PV = nRT
2.1*10^-4m^3 Times 5.3*105Pa = n * Gas Constant * Temperature
2.1*10^-4m^3 (*) 5.3*105Pa = # of moles *

I'm not sure what I was doing, but the whole equation stuff got hard and I stopped.
I left this question for 3 days, so I thought that I might ask for help.

 

[Ssnow]

2.1*10^-4m^3 Times 5.3*105Pa = n * Gas Constant * Temperature

You must invert the formula finding the number of moles $n$, and after the number of atoms...
Ssnow

 

[Chandra Prayaga]

In your ideal gas equation

pV = nRT

all the quantities are given, except n. So solve for n. That is the first step. Now to nswer (ii), you need to know how many atoms thyere are in one mole of the ideal gas. Do you know that?