Map University Science Books presented by Sapling Learning General Chemistry 4th

Question

Map University Science Books presented by Sapling Learning General Chemistry 4th Editioo Vitamin K is involved in normal blood clotting. When 1.11 g of vitamin K is dissolved in 25.0 g of camphor, the freezing point of the solution is lowered by 3.71 . The freezing point and Kf constant for camphor can be found here. Calculate the molar mass of vitamin K Number 4532.78 g/ mol There is a hint available w the hint by clicking on the tom divider bar. Click on the der bar again to hide the hint. Close O Previous O Check Answer Next

Explanation / Answer

depression in freezing point = Kf (for solvent) X m ( of solution)

since freezing point is lowered by 3.71 degree C
so depression in freezign point = 3.71
here solvent in camphor and solution is made up of vitamin k (solute) and camphor (solvent)

Kf for camphor = 37.7 degree C/m

given that camphor = 25 g = 0.025 kg

m = no.of moles of vitamin k/amount of camphor(solvent) in kg = no.of moles of vitamin k(solute)/0.025

putting the values...
3.71 = 37.7 X no.of moles of vitamin k(solute)/0.025

3.71 = 1508 X no.of moles of vitamin k

no.of moles of vitamin k = 3.71/1508 = 2.46 X 10^-3

amount of vitamin K = 1.11 g
and no.of moles of vitamin k = mass of vitamin k /molar mass of vitamin k = 2.46X 10^-3

1.11 /molar mass of vitamin k = 2.46 X 10^-3

molar mass of vitamin k = 1.11/2.46 X 10^-3 = 451.22 g/mole

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