How do I calculate the volume of a gas?

How to Calculate Gas Volume

• Answer:

  Are you transformed back to childhood when you watch a helium balloon drift into the sky? Well, you're not alone in that fascination. Since the 19th century development of the latex balloon, worldwide audiences have been delighted by their properties. Scientists developed balloons based on a core scientific principle -- gas volume. Understanding gas volume helps you determine how big a balloon can be, how high it might fly or what kind of gas should go inside of it. You too can begin to address these questions by first learning how to calculate gas volume. Difficulty: Moderate Things You'll Need Calculator Instructions Understand the formula's variables. A theorem called the Ideal Gas Law allows you to calculate the volume of a gas. It is written as PV=nRT. The gas volume (V) depends on the temperature in Kelvins (T), the pressure in your system (P), and the amount of gas you have in moles (n). It also requires you to use a value called the gas constant (R), which is equal to 0.08206 in units of atmL/molK. Some equations will allow you to use standard temperature and pressure. That would mean T equals 273 degrees Kelvin and pressure would equal 760 torr. Plug in the available values. Since you have the value for R, if you know three of the other variables in the equation, you can use algebra to solve for the 4th variable. Lets try a typical example. What volume of gas would you need to give 3 grams of helium gas, a pressure of 800 torr at 296 degrees kelvin? Here you have been given the amount (n), the pressure (P) and the temperature (T). You can now begin to solve for the volume (V). Convert torr to atm. Because you need your final answer to be in units of liter, you should convert your units of pressure, so that when all units cancel out, only the unit of liters will be left. This means converting pressure in torr to atm. Each atm = 760 torr. Divide 800 by 760 to get (P). It should equal .95 atm. Convert grams to moles. For this equation, you need to convert grams of helium to moles. To make this conversion you need to consult with a periodic table to find its molar mass. The molar mass of helium is 4 g/mol. If we have 3 grams of helium that means our (n) is .75 moles. Solve for the volume. To get the volume of gas, multiply the moles of helium (n), by the gas constant (R) and the temperature (T). Divide that product by the pressure (P). In our helium example it would appear as: V=nRT/P or V=(.75 x .08206 x 296)/.95. After completing this calculation you should find that your volume of helium equals =19.17 liters.