Question #4760a Chemistry Gases Ideal Gas Law 1 Answer Stefan V. Dec 18, 2014 The video shows an application of the ideal gas law, #PV = nRT#. In order to solve for mass, we first need to determine what the number of moles of gas is; keep in mind that #R#'s units are #(L * atm)/(mol * K)#. So, #n = (PV)/(RT) = (1.80 atm * 3.00L)/(320K * 0.082 (L * atm)/(mol * K)# Let's isolate the #R# constant #n = (1.80 atm * 3.00L)/(320K) * 1/(0.082 (L * atm)/(mol * K))# We know that #1/(A/B) = 1 * (A/B)^(-1) = B/A#, and we can apply this to units as well #1/(0.082) * 1/((L * atm)/(mol * K)) = 1/(0.082) * (mol * K)/(L * atm)# This is why (mol * K) moves to the numerator. The equation now becomes #n = (1.80 atm * 3.00L)/(320K) * ( 1 mol * K)/(0.082 L * atm)# atm, L, and K are cancelled out since they're both on the numerator, and on the denominator, and the answer becomes #n = ( 1.80 * 3.00 mol)/( 320 * 0.082) = 0.206# moles Related questions How do you find the ideal gas constant? How do you solve ideal gas law problems? How do you know which ideal gas constant to use? What is the ideal gas constant for butane? Why is ideal gas law in kelvin? Why is the ideal gas constant important? What is the di-electric constant? What volume (L) will 0.20 mol HI occupy at 300 K and 100.0 kPa? R = 8.314 kPa L / (K mol) = 0.08205 ... How do you calculate the molar mass of a gas? When should I use the ideal gas law and not the combined gas law? See all questions in Ideal Gas Law Impact of this question 200 views around the world You can reuse this answer Creative Commons License