Science, Tech, Math › Science Ideal Gas Law Example Problem Find Moles of Gas Using the Ideal Gas Law Share Flipboard Email Print At low temperatures, real gases act like ideal gases. Jessica Peterson/Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Todd Helmenstine Todd Helmenstine is a science writer and illustrator who has taught physics and math at the college level. He holds bachelor's degrees in both physics and mathematics. our editorial process Todd Helmenstine Updated January 20, 2019 The ideal gas law is an equation of state the describes the behavior of an ideal gas and also a real gas under conditions of ordinary temperature and low pressure. This is one of the most useful gas laws to know because it can be used to find pressure, volume, number of moles, or temperature of a gas. The formula for the ideal gas law is: PV = nRT P = pressureV = volumen = number of moles of gasR = ideal or universal gas constant = 0.08 L atm / mol KT = absolute temperature in Kelvin Sometimes, you may use another version of the ideal gas law: PV = NkT where: N = number of moleculesk = Boltzmann constant = 1.38066 x 10-23 J/K = 8.617385 x 10-5 eV/K Ideal Gas Law Example One of the easiest applications of the ideal gas law is to find the unknown value, given all the others. 6.2 liters of an ideal gas is contained at 3.0 atm and 37 °C. How many moles of this gas are present? Solution The ideal gas law states PV = nRT Because the units of the gas constant are given using atmospheres, moles, and Kelvin, it's important to make sure you convert values given in other temperature or pressure scales. For this problem, convert °C temperature to K using the equation: T = °C + 273 T = 37 °C + 273T = 310 K Now, you can plug in the values. Solve ideal gas law for the number of moles n = PV / RT n = ( 3.0 atm x 6.2 L ) / ( 0.08 L atm /mol K x 310 K)n = 0.75 mol Answer There are 0.75 mol of the ideal gas present in the system.