Question

the internal energy of an ideal gas depends on

Answer 1

"the internal energy of a fixed mass of ideal gas is a function only of its temperature"
From Wikipedia.
http://en.wikipedia.org/wiki/Ideal_gas

That does also mean if you have more of the gas there will be more energy "total". However most of the time you are comparing equal amounts of gas.

Answer 2

Yes, proportional to the # of moles of gas and the absolute temperature.