Use the ideal gas law
Find the volume of a gas from PV = nRT, with moles, temperature and pressure.
The ideal gas law says PV = nRT. Rearranged for volume, V = nRT ÷ P.
With R = 0.0821 L·atm/(mol·K), n = 2 mol, T = 300 K (use kelvin, never °C) and P = 1 atm: V = 2 × 0.0821 × 300 ÷ 1 = 49.26 litres.
Classic Graphing 84
Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.
Type n × R × T ÷ P with the numbers: 2 × .0821 × 300 ÷ 1.
2×.0821×300÷1Press enter. The volume is 49.26 litres.
enter
You should see49.26
Natural Scientific 991
Start on the main screen: Press MENU, then 1 (Calculate) to return to the main calculation screen. AC clears the line you are on.
Type 2 × .0821 × 300 ÷ 1.
2×.0821×300÷1Press = . The answer first appears as a fraction, so press S⇔D to see the decimal.
=S⇔D
You should see49.26
RPN Scientific 15
Start on the main screen: There is no menu to leave. Press the back arrow to clear a number you are typing, or CLx (g then back arrow) to clear the X register.
Key in n, ENTER, then R and press ×.
2ENTER.0821×Key in T and press ×, then key in P and press ÷.
300×1÷
You should see49.2600
Tips
- Convert °C to kelvin first: K = °C + 273.15.
- Match the units of R to your pressure and volume units. 0.0821 goes with atm and litres; 8.314 goes with pascals and cubic metres.
Related guides
- Use a physical constant in a formulaEnter constants such as the speed of light correctly, store them for reuse, and see them in the Units lab.
- Calculate molar massAdd up the atomic masses of every atom in a formula, like glucose C₆H₁₂O₆, to get grams per mole.
- Convert between unitsChange miles per hour to metres per second (or any unit) by multiplying by conversion factors.