Question

Which would have a greater impact on the freezing point depression of ice, CrF3 or CaF2? Explain briefly.

Answer 1

Answer:
`CrF_3` has greater impact on the freezing point depression of ice.

Step-by-step explanation:

Depression in freezing point is given by:

`\Delta T_f=i* K_f* m`

`\Delta T_f=T_f-T_f^0` = Depression in freezing point

i= vant hoff factor

`K_f` = freezing point constant

m= molality

`\Delta T_f=i* K_f* \frac{\text{mass of solute}}{\text{molar mass of solute}* \text{weight of solvent in kg}}`

a) i = 4 for
`CrF_3` as it dissociates to give 4 ions in water.

`CrF_3\rightarrow Cr^(3+)+3F^-`

b) i = 3 for
`CaF_2` as it dissociates to give 3 ions in water.

`CaF_2\rightarrow Ca^(2+)+2F^-`

As the vant hoff factor is higher for
`CrF_3` , it has greater impact on the freezing point depression of ice.