CBSE Class 12 · 2003 · All India · SolutionsShort Answer

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What is meant by van't Hoff factor? The osmotic pressure of a 0.0103 molar solution of an electrolyte is found to be 0.70 atm at 27°C. Calculate the van't Hoff factor. What conclusion do you draw about the molecular state of the solute in the solution? (R = 0.082 L atm mol

^{- 1}

^{- 1}

)

Solution

van't Hoff factor:

i = \frac{observed colligative property}{calculated (normal) value}

Calculated osmotic pressure:

π_{c a l c} = C R T = 0.0103 \times 0.082 \times 300 = 0.2534 atm

i = \frac{0.70}{0.2534} = 2.76

Since

i > 1

, the solute is dissociated in solution — the value near 3 indicates it furnishes about three ions per formula unit.

CBSE Class 12 Board · 2003 · All India · Subjective

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