How do you find the number of moles for a gas from temperature and pressure?

Question

Wyatt Atkins · Accepted Answer

You use the Ideal Gas Law.

The volume is also necessary. The number of moles is then determined by entering the pressure, volume, and temperature into the expression. The ideal gas law is #color(blue)(bar(ul(|color(white)(a/a)pV = nRTcolor(white)(a/a)|)))" "# We can rearrange this formula to get the number of moles, #n#. #n = (pV)/(RT)# AN EXAMPLE Neon gas in a 3.00 L container at 27 °C and 770 mmHg is present. How many moles of neon are there? Resolution Step 1: List the provided data, converting it as needed. #p = 770 color(red)(cancel(color(black)("mmHg"))) × "1 atm"/(760 color(red)(cancel(color(black)("mmHg")))) = "1.013 atm"# #V = "3.00 L"# #R = "0.082 06 L·atm·K"^"-1""mol"^"-1"# #T = "(30 + 273.15) K = 303.15 K"# Step 2: Determine the mole count. #n = (1.013 color(red)(cancel(color(black)("atm"))) × 3.00 color(red)(cancel(color(black)("L"))))/("0.082 06" color(red)(cancel(color(black)("L·atm·K"^"-1")))"mol"^"-1" × 300.15 color(red)(cancel(color(black)("K")))) = "0.123 mol"# Neon has a mass of 0.123 mol in the container.

Cooper Adams · Answer

undefined You can find the number of moles of a gas from temperature and pressure using the ideal gas law equation:

n = (PV) / (RT)

Where:
n = number of moles
P = pressure (in atm)
V = volume (in liters)
R = ideal gas constant (0.0821 L·atm/mol·K)
T = temperature (in Kelvin)

Ensure the units for pressure and volume are consistent with the ideal gas constant.