What would the final freezing point of water be if 3 mol of sugar were added to 1 kg of water (kf = 1.86c/(mol/kg) for water and i = 1 for sugar)?

is this for a test or are you genuinely interested? molality = mols sugar/kg solvent

Solve for molality

delta T = Kf*m

Solve for delta T and subtract from zero C to find the new freezing point.

or

-5.58

The final freezing point of water is -5.58

Explanation:

According to colligative properties of molecules,

where is the depression in freezing point of a solution, i is the vant hoff factor of solute, is the cryogenoscopic constant of solvent and m is molality of the solution.

Here solute is sugar and solvent is water.

Molality of solution = = = 3 mol/kg

So = -5.58