LabBench Activity

Analysis of Results

So that you might better understand the procedure for calculating water potential, here is a practice problem.

Once you know the solute concentration, you can calculate solute potential using the following formula:

Solute potential (Ψs) = −iCRT

i = The number of particles the molecule will make in water; for NaCl this would be 2; for sucrose or glucose, this number is 1

C = Molar concentration (from your experimental data)

R = Pressure constant = 0.0831 liter bar/mole K

T = Temperature in degrees Kelvin = 273 + °C of solution

Sample Problem

The molar concentration of a sugar solution in an open beaker has been determined to be 0.3M. Calculate the solute potential at 27 degrees. Round your answer to the nearest hundredth.

The pressure potential of a solution open to the air is zero. Since you know the solute potential of the solution, you can now calculate the water potential. (If you need to, review the equation for calculating water potential.)

What is the water potential for this example? Round your answer to the nearest hundredth.