Kind of a "silly" gas question

[September24]

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When it comes to the ideal gas law (PV=nRT), does changing any of the variables (aside from n) change the number of moles?

To my knowledge, when moles increase, pressure increases. However, technically,an increase in a pressure does not increase moles correct? An increase of pressure could happen BECAUSE OF an increase in moles but a volume or pressure increase does not change moles.

The same is true for temperature right? A pressure increase will have happened because of an increase in temperature but a temperature increase doesn't increase pressure directly?

Does anyone know the confusion I'm having here? Will the MCAT try to trick me up like that?

 

[Sammy1024]

Yes. Pressure increase doesn't increase moles (as long as it's a closed system, where nothing can enter).
Temperature increase can affect pressure. Ex: If the volume doesn't change, then T increase causes a P increase.
The MCAT will totally try to trick everyone like that. I would be surprised if it didn't do that in the answer choices.

 

[September24]

Right. As temperature increases, the gas will have more kinetic energy and will hit the walls with more force thus increasing pressure. On the other hand, simply reducing volume or increasing pressure will not randomly give the gas energy right? So pressure cannot increase temperature?

 

[SweetBurger]

idk if you allowed to post links but you should go look up a PV=nRT calculator on google and pick a variable to solver for and see the different factors that affect it.

 

[Mad Jack]

Right. As temperature increases, the gas will have more kinetic energy and will hit the walls with more force thus increasing pressure. On the other hand, simply reducing volume or increasing pressure will not randomly give the gas energy right? So pressure cannot increase temperature?

A change in pressure sure as hell will change the temperature of a gas- it's freakin' Gay-Lussac's Law. Learn the laws mayne, or learn how to do the algebra like a boss. Charle's Law, Boyle's Law, Gay-Lussac's Law, and the Ideal Gas Law can get you through basically any questions involving gasses.

 

[Sammy1024]

All you need to know is PV = nrT and that r doesn't change and n usually doesn't change (as long as it's in a closed system).

If P goes up something has to change for the stuff to still equal to eachother so either V goes down or T goes up.

Ex: P = 2, V = 3, T = 6

If P is now 3... 3 x 3 = 9 but T is only 6! So either the value of V decreased to 2 or the value of T increases to 9.

 

[medic86]

PV=nRT = my favorite equation. 😀