Which of these solutions has the highest freezing point?

1.0 m molecular sucrose (c12h22o11)

1.0 m ionic sodium chloride (nacl)

1.0 m ionic calcium bromide (cabr2)

1.0 m ionic aluminum bromide (albr3)

1.0 m ionic potassium chloride (kcl)

Option (a) is the correct answer.

Explanation:

Depression in freezing point depends on Vant Hoff factor. So, more is the number of dissociated ions lesser will be the freezing point.

Mathematically,      

where   = freezing point depression

                             i = Vant Hoff factor

                = freezing point depression

                           m = molality of the solution      

The ratio between concentration of particles that are actually produced when a substance is dissolved and the concentration of a substance calculated from its mass is known as Vant Hoff factor.

Mathematically,    i =

For dissociation i is greater than or equal to 1.  1 then dissociation has taken place. When i = 1 then neither association or dissociation has taken place.  

Hence, sucrose will have i = 1 as it produces only one ion.

Sodium chloride will have i = 2 as it produces two ions.

Calcium bromide will have i = 3 as it produces three ions.

Aluminium bromide will have i = 4 as it produces four ions.

Potassium chloride will have i = 2 as it produces two ions.

Therefore, we can conclude that sucrose solution will have highest freezing point.