Convert L·atm (liter-atmospheres) to joules, or calculate pressure-volume work in joules from a pressure in atm and a volume change in liters.
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Joules from L·atm (Pressure–Volume) Formula
The following example problem outlines the steps and information needed to calculate joules from a pressure–volume value. Note: atm is a unit of pressure, so you need a volume (or an L·atm value) to convert to energy.
Variables:
- J is the energy (joules, J)
- L·atm is the pressure–volume product in liter-atmospheres (atm·L)
To convert liter-atmospheres (L·atm) to joules, multiply by 101.325. If you have pressure in atmospheres and volume in liters, first compute L·atm = P(atm) × V(L). For constant-pressure work, use the volume change (final minus initial). Work magnitude is |P × ΔV|; work on the gas uses w = −P × ΔV, so expansion is negative and compression is positive. Magnitude inverse calculations use the positive expansion branch. Calories use the thermochemical definition; BTU uses the International Table definition.
| L·atm | Joules (J) |
|---|---|
| 1/16 | 6.333 |
| ⅛ | 12.666 |
| 1/6 | 16.888 |
| ¼ | 25.331 |
| ⅓ | 33.775 |
| ⅜ | 37.997 |
| ½ | 50.663 |
| ⅝ | 63.328 |
| ⅔ | 67.550 |
| ¾ | 75.994 |
| ⅞ | 88.659 |
| 1 | 101.325 |
| 1¼ | 126.656 |
| 1⅓ | 135.100 |
| 1½ | 151.988 |
| 1¾ | 177.319 |
| 2 | 202.650 |
| 2½ | 253.313 |
| 3 | 303.975 |
| 4 | 405.300 |
| * Rounded to 3 decimals. Exact factor: 1 L·atm = 101.325 J (since 1 atm = 101.325 kPa). | |
How to Calculate Joules from L·atm?
The following steps outline how to calculate joules from L·atm.
- First, determine the pressure–volume product in L·atm (if needed, compute L·atm = P(atm) × V(L)).
- Next, use the formula from above: J = (L·atm) × 101.325.
- Finally, calculate the energy in joules.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Total PV = 30 L·atm
J = (L·atm) × 101.325 = 30 × 101.325 = 3039.75 J
