Ideal Gas Law Formula

The Ideal Gas Law was created to show the relationship between pressure, volume, number of moles of gas and temperature. It is a combination of Boyle's Law and Charles' Law. It shows the equation of a hypothetical ideal gas. Pressure and volume have an inverse relationship with each other (when 1 goes up the other goes down) but have a direct relationship with Temperature (when they go up, temperature goes up)

The equation for the Ideal Gas Law is:

PV = nRT

P = Pressure (atm)

V = Volume (Liters – L)

n = Number of moles (mol)

R = The Ideal Gas Constant (0.08206 L-atm/mol-K)

T = Temperature (Kelvin)

Ideal Gas Law Formula Questions:

1.) How many moles of gas are contained in 890.0mL at 21 °C and 750mm Hg?

Answer: The Volume is V = 890.0mL and the Temperature is T = 21°C and the Pressure is P = 750mmHg.

To use the Ideal Gas Law Equation, you must covert Volume to Liters, Temperature to Kelvin and Pressure to Atmosphere.

V = 890mL/1000 = 0.89L

T = 21°C + 273 = 294K

P = 750mmHg/760 = 0.987atm

Plug into the Idea Gas Law Equation

PV = nRT

0.987atm(0.890L) = n(0.08206L-atm/mol-K)(294K)

n = 0.037moles

There are 0.037moles of gas contained.

2.) Calculate the volume 3.00 moles of a gas will occupy at 24°Celsius and 762.4 mm Hg.

Answer: The number of moles is n = 3.00moles, temperature is T = 24°C and pressure is P = 762.4 mmHg

To use the Ideal Gas Law Equation, you must convert Temperature to Kelvin and Pressure to Atmospheres.

T = 24 + 273 = 297K

P = 762.4/760 = 1.003atm

Plug into the Ideal Gas Law Equation

PV = nRT

1.003atm(V) = 3.00moles(0.08206L-atm/mol-K)(297K)

V = 72.897L

The volume of the gas would be 72.897 Liters