Which of the following solutes will lower the freezing point of water the most?
a.
the molecular compound sucrose (c12h22o11)
b.
the ionic compound magnesium sulfate (mgso4)
c.
the ionic compound lithium chloride (licl)
d.
the ionic compound calcium fluoride (caf2)

D.  the ionic compound calcium fluoride

The correct option here is the fourth one.

Explanation:

Salt like compounds addition to water is likely to be inducing certain changes in temperature of freezing into solid and also alter the temperature of boiling.  

It is noticed that addition of salts in water mostly tends to get lower the freezing temperatures from the original freezing point of water and among the given 3 options calcium fluoride tends to lower the freezing point most when compared to others.

Thus as vant hoff factor is highest factor for and the freezing point will be lowest.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

i think the answer is terrae but not 100 percent sure. ▓▬▬ §