The equation to determine the osmotic pressure is = M R T , where is the osmotic

Question

The equation to determine the osmotic pressure is =MRT, where is the osmotic pressure, M is the molarity (molar concentration) of the solution, R is the universal gas constant (0.08206 Latmmol1K1), and T is the temperature on the Kelvin scale. When determining the osmotic pressure you also take into account the number of particles present in the solution for ionic substances. The correlation between the osmotic pressure and the number of particles for ionic substances is expressed in terms of a factor known as van't Hoff’s factor, i. This factor is the ratio of the number of ions in a solution per formula unit.

For NaCl, the expected factor is 2.0 but the actual value is less than 2.0 as cations may combine with anions in the solution.

Thus, the formula for determining osmotic pressure is =iMRT.

1. The osmotic pressure, , of a solution of glucose is 31.8 atm . Find the molarity of the solution at 298 K.

Explanation / Answer

i = 2 for NaCl

R = 0.08206 L-atm / mol K

T = 298 K

= 31.8 atm

= i MRT

31.8 = 2 x M x 0.08206 x 298

M = 0.650

molarity = 0.650 M -----------------------> answer

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