# calculating-water-potential-worksheet-2014_1.docx -...

• 4

This preview shows page 1 - 2 out of 4 pages.

Calculation of Water Potential from Experimental Data Name _ Date Per 1. The solute potential of this sucrose solution can be calculated using the following formula: ψ s = -iCRT where i = Ionization constant (for sucrose this is 1.0 because sucrose does not ionize in water) C = Molar concentration (determined from your graph – see your potato data) R = Pressure Constant (R = 0.0831 liter bars/mole ° K) T = Temperature ( ° K) (273 + ° C of solution) The units of measure will cancel as in the following example: A 1.0 M sugar solution at 22 ° C under standard atmospheric conditions ψ s = -i X C X R X T ψ s = -(1)(1.0 mole/liter)(0.0831 liter bar/mole K)(295 K) ψ s = -24.51 bars 2. Knowing the solute potential of the solution (ψ s ) and knowing the pressure potential of the solution is zero p = 0) allows you to calculate the water potential of the solution. The water potential will be equal to the solute potential of the solution. Ψ = 0 + ψ s or ψ = ψ s The water potential of the solution at equilibrium will be equal to the water potential of the potato cells. What
• • • 