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Question 11.13: USING OSMOTIC PRESSURE TO CALCULATE THE MOLARITY OF A SOLUTI...

USING OSMOTIC PRESSURE TO CALCULATE THE MOLARITY OF A SOLUTION

A solution of an unknown substance in water at 293 K gives rise to an osmotic pressure of 5.66 atm. What is the molarity of the solution?

STRATEGY

We are given values for \Pi and T , and we need to solve for M in the equation \Pi = MRT.

Rearranging this equation, we get

M = \frac{\Pi}{RT}

where \Pi = 5.66 atm, R = 0.082 06(L · atm)/(K · mol), T = 298 K.

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M = \frac{5.66  atm}{\left(0.082  06 \frac{L  ·  atm}{K  ·  mol} \right)(293  K)} = 0.235 M

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