Question

Which of the following solutes will lower the freezing point of water the most?

A) the molecular compound sucrose (C₁₂H₂₂22O₁₁)

B) the iconic compound magnesium sulfate (MgSO₄4)

C)the iconic lithium chloride (LiCI)

D)the iconic compound calcium fluoride(CaF₂2)

Answer 1

D) the iconic compound calcium fluoride (CaF₂)

Step-by-step explanation:

I took the test and got it right

Answer 2

Answer: D) the iconic compound calcium fluoride (CaF₂)

Explanation:

`\Delta T_f=i* k_f* m`

where,

`\DeltaT_f` = change in freezing point

i= vant hoff factor

`k_f` = freezing point constant

m = molality

A) the molecular compound sucrose (C₁₂H₂₂O₁₁)

: For non electrolytes like sucrose, vant hoff factor is 1.

B) the iconic compound magnesium sulfate (MgSO₄): For electrolytes, vant hoff factor is equal to the number of ions it produce on dissociation.

`MgSO_4\rightarrow Mg^(2+)+SO_4^(2-)` Thus i= 2

C) the iconic lithium chloride (LiCI):

`LiCl\rightarrow Li^++Cl^-`, thus i=2.

Thus 1% produces most ions and thus lowers the freezing point to maximum.

D) the iconic compound calcium fluoride(CaF₂):

`CaF_2\rightarrow Ca^(2+)+2F^-`, thus i=3.

Thus the compound with highest value of i, will depress the freezing point to maximum.