What mass of ethanol must be added to 10.0L of water to five a solution that freezes at -10.0 degrees C. Assume the density of water is q.00 g/mL. Kf of water is 1.86 degrees C/m.

Answer 1

You made a typo on the density of water in your post. Also, I don't understand the expression "to FIVE a solution that". I assume FIVE should be FIND.
delta T = Kf*molality
delta T = -10
Kf you know.
Solve for molality
definition of molality = mol/kg solvent.
You know molality and kg solvent, solve for mol ethanol.
Then mol ethanol = g/molar mass.
You know mol and molar mass. Solve for grams.