Question

how and when to use van der waals equation? \[(P + \frac{an^2}{V^2})(V - nb) = nRT\]

Answer 1

what do the variables mean? and also how and when do i use it?

Answer 2

a and b are variables unique to the gas at a certain temperature. P is pressure, V is volume, n is number of moles, T is temperature, R is gas constant. You'd want to use this over the Ideal Gas Law equation is the gas enclosed is under a high amount of pressure and/or the temperature of the gas is lower, although there's no rule of thumb on when to use it.

Answer 3

can you clarify this statement "You'd want to use this over the Ideal Gas Law equation is the gas enclosed is under a high amount of pressure and/or the temperature of the gas is lower"

Answer 4

im seeing so many is...

Answer 5

@dominusscholae you there?

Answer 6

Yeah. Basically I should have said "the pressure of the gas is high enough and/or the temperature is low enough to make the Ideal Gas Law invalid in this case."

Answer 7

so you're saying that when there's a high pressure or a low temperature then the ideal gas law is invalid?

Answer 8

Yes. The extent of each condition though has to be great enough, though. Like I said, there's no rule of thumb on whether one should use the Ideal Gas Law equation or van der Waals equation, but generally if a question says "high pressure/low temperature" use the van der Waals.

Answer 9

...so now im confused when the ideal gas law is used o.O

Answer 10

anyway...the n and V in an^2/V^2 are moles and volume right?

and the n in nb is moles too?

Answer 11

Yes. For the sake of easing your trouble, use the Ideal Gas Law when the gas is under "high temperature and low pressure".

Answer 12

lol this really confirms my theory that chemistry is so confusing and screwed :P hahaha lol

Answer 13

XD. Don't worry about it. Lot's of people hate this. It's only second to physics for many in terms of hate.

Answer 14

lol dont forget math =))