Copy_of_Water_Potential_Problems_HWstudent - Name Crystal...

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Name: Crystal Leonard Date: 10/22/20 Period: 2 Water Potential Problems The solute potential (ψ S ) = – iCRT, where i is the ionization constant, C is the molar concentration, R is the pressure constant (R = 0.0831 liter bars/mole-K), and T is the temperature in K (273 + °C). Example 1 : A 0.15 M solution of sucrose at atmospheric pressure (ψ P = 0) and 25°C. S ) = – iCRT C= 0.15 M T= (273 +25) R= 0.0831 i= 1 (this is because sucrose doesn’t disassociate in water) ψ S = - (1)(0.15)(0.0831)(273+25) = -3.7 bars This example has an osmotic potential of -3.7 bars Ψ s + Ψ p = Ψ Ψ = 0 + -3.7 bars = -3.7 bars Example 2 : A 0.15 M NaCl solution contains 2 ions, Na + and Cl - ; therefore i = 2. Room Temperature of 25°C. S ) = – iCRT i=2 C= 0.15 M R= 0.0831 T= (273 +25) S )= -(2)(0.15)(0.0831)(298) = -7.4 bars Next: Ψ = 0 + -7.4 bars =-7.4 bars Careful when answering these questions: Which of the above has MORE water potential? Example 1 Which of the above is MORE concentrated? Example 2

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