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 )

Step-by-step solution

HCOOH = 0 . 5 ml   L - 1 ⇒ 0 . 5 ml × 1 . 05   g   ml - 1   HCOOH in 1   L ⇒ 0 . 525   g   HCOOH in 1   L Weight of water will be   =   1   kg   since   density   of   water   is   1   kg / L m = 0 . 525 46 1   kg   mol [Assuming dilute solution] ∴   ΔT f = iK f m ⇒ i = ΔT f k f m = 0 . 0405 × 46 1 . 86 × 0 . 525 = 1 . 9