Osmosis occurs when two solutions of different concentrations are separated by a

Question

Osmosis occurs when two solutions of different concentrations are separated by a semipermeable membrane. The membrane allows solvent particles, but not solute particles, to pass through. Thus, the solvent moves toward the solution of higher concentration (to dilute it) until the two solutions have the same concentration, or until gravity overtakes the osmotic pressure, II. The osmotic pressure between a solution and pure solvent depends on the number of solute particles and thus is a colligative property. It can be expressed as II = MRT where M is the total molarity of the solute particles, R = 0.08206 L atm/(K mol) is the gas constant, and T is the Kelvin temperature. Isotonic saline solution, which has the same osomotic pressure as blood, can be prepared by dissolving 0.923 g of NaCl in enough water to produce 100. mL of solution. What is the osmotic pressure of this solution at 25 degree C? Express your answer to three significant figures and include the appropriate units. This question will be shown after you complete previous question(s). Osmosis is the process responsible for carrying nutrients and water from groundwater supplies to the upper parts of trees. The osmotic

Explanation / Answer

m = 0.923 g NaCL

V = 100 ml

osmotic pressure at 25ªC

= MRT

= pressure in atm

M = molarity in mol/L

R = 0.082 Latm/molK

T = temperature in K

M = mol/V

mol of NaCl = mass/MW = 0.923/58 = 0.01591

M = 0.01591 / 0.1 = 0.1591 M of NaCl

NOTE that we need to account for 2 particles: Na+ and Cl- therefore

M = 2X = 2*0.1591 = 0.3182 M

Substitute

= MRT = 0.3182*0.082*298 = 7.78 atm

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