An unknown amount of gas has a volume of 12 L and a pressure of 5.6 atm. If the temperature is 205K, how many moles of gas are present?

Answer 1

Use the Ideal Gas Law, PV=nRT, to solve this problem.

Since you are trying to find moles,you are solving for n, so rearrange the equation for n by dividing both sides by RT. This gives you n = PV / RT

R is a gas law constant and is always equal to 0.0821 Latm/molK. The other variables are given in your problem.

n = (5.6 atm)(12L) / (0.0821 Latm/molK)(205 K) = 3.9928 mol or rounded to significant figures: 4.0 moles.