Cyclohexane has a freezing point of 6.50 ∘C and a Kf of 20.0 ∘C/m. What is the freezing point of a solution made by dissolving 0.771 g of biphenyl (C12H10) in 25.0 g of cyclohexane?

Explanation:

Depression in freezing point is:

where,

= freezing point of solution = ?

=  freezing point of solvent (cyclohexane) =

=  freezing point constant  of  solvent (cyclohexane)  =

m = molality

i = Van't Hoff factor = 1 (for non-electrolyte)

= mass of solute (biphenyl) = 0.771 g

= mass of solvent (cyclohexane) = 25.0 g

= molar mass of solute (biphenyl) =

Now put all the given values in the above formula, we get:

Therefore, the freezing point of a solution made by dissolving 0.771 g of biphenyl in 25.0 g of cyclohexane is

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.

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