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How to Calculate Solute Potential

Updated February 21, 2017

In biology, potential refers to a pressure that determines the direction a given substance will flow. For example, water travels from areas of higher potential to areas of lower potential. The same is true for a solute, or a substance mixed into a solution. One example of this is a material moving in and out of cells. Solute potential depends on the number of particles the solute breaks into in the solution, solution molarity and temperature. Molarity describes the number of moles of solute in the solution per litre. One mole of a substance corresponds has a mass, in grams, equal to its atomic mass from the periodic table.

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  1. Convert the temperature of the solution to degrees Kelvin by adding 273 to its Celsius temperature. For example, a temperature of 20 degrees Celsius corresponds to 293 degrees Kelvin.

  2. Determine how many particles the solute will make in the solution by consulting a chemistry table. For example, for sodium chloride (NaCl), the number is 2.

  3. Multiply the particle number times the solution molarity times the pressure constant times the temperature to obtain the solute potential in bars. The pressure constant is 0.0831 litres times bar per mole per Kelvin. A bar is a unit for pressure. Assuming a molarity of 10.0 moles per litre, you have 2 times 10.0 moles per litre times 0.0831 litres times bar per mole per Kelvin times 293 Kelvin, which equals a solute potential of 487.0 bars.

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About the Author

William Hirsch started writing during graduate school in 2005. His work has been published in the scientific journal "Physical Review Letters." He specializes in computer-related and physical science articles. Hirsch holds a Ph.D. from Wake Forest University in theoretical physics, where he studied particle physics and black holes.

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