Water potential (psi) = pressure potential + solute potential. For an open beaker at 25 C, pressure potential = 0, so psi = solute potential = -iCRT, where i is the ionization constant (1 for sucrose), C is molarity, R = 0.0831 (L bar)/(mol K), T = 298 K. The potato cylinders showed isotonic mass change at 0.2 M sucrose.
What is the calculated water potential of the potato cells?
- A
About 0 bars
- Bcheck_circle
About -4.95 bars
- C
About -2.50 bars
- D
About -10.0 bars
Explanation
psi = -(1)(0.2)(0.0831)(298) = -4.95 bars. At isotonic equilibrium, the potato cell water potential matches the external 0.2 M solution.