1. Tardigrade
  2. Question
  3. Chemistry
  4. The depression in freezing point observed for a formic acid solution of concentration 0.5 mL L -1 is 0.0405° C. Density of formic acid is 1.05 g mL -1. The Van't Hoff factor of the formic acid solution is nearly: (Given for water k f =1.86 K kg mol -1 )

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Q. The depression in freezing point observed for a formic acid solution of concentration $0.5\, mL\, L ^{-1}$ is $0.0405^{\circ} C$. Density of formic acid is $1.05 \, g \, mL ^{-1}$. The Van't Hoff factor of the formic acid solution is nearly : (Given for water $k _{ f }=1.86 \, K \, kg \, mol ^{-1}$ )

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Solution:

${[ HCOOH ]=0.5 \,ml ^{-1}} $
$ \Rightarrow\left(0.5\, ml \times 1.05 \,g \,ml ^{-1}\right) HCOOH \text { in } 1 L $
$ \Rightarrow 0.525 \,g \,HCOOH$ in $1 L $
$ m =\frac{(0.525 / 46)}{1 \,kg } mol$
[Assuming dilute solution]
$\therefore \Delta T _{ f }= iK _{ f } m \Rightarrow i =\frac{\Delta T _{ f }}{ k _{ f } m }=\frac{0.0405 \times 46}{1.86 \times 0.525}=1.9$