A solution of 2.5 g of a compound having the emperical formula C6H5P in 25 g of C6H6 is observe to freeze?

Question

at 4.3 degree Celcius. what is the molar mass of the solute and its molecular formula

Answer 1

Kf of benzene = 5.12

freezing point benzene =5.5 °C

delta T = 5.5 - 4.3 =1.2

1.2 = 5.12 x m

m = 0.234 = moles / 0.025 Kg

moles = 0.00586

MM = 2.5 g / 0.00586 = 426.7 g/mol

Molar mass C6H5P = 108.0798 g/mol

426.7 / 108.0798 = about 4

C24H 20P4 is the molecular formula