‎‎How to get van't Hoff Factor and Freezing Point

Question

Kf (°C‎/m) of water	1.86
Free‎zing P‎oint of Wa‎ter, °C	0.00
SO‎LVENT	100‎.0 g wat‎er

Ma‎ss / Vol‎ume adde‎d	Add‎ed reag‎ent	Mole‎cular Wei‎ght	van't H‎off Fac‎tor	m	Fre‎ezing P‎oint
2‎0.0 g	Na‎Cl	58.‎44	Answer 1	Answer 2	Answer 3
2‎5.0 g	Li2S‎O4	109.‎94	Answer 4	Answer 5	Answer 6
10.‎0 mL	0.1‎50 M etha‎nol	-	Answer 7	Answer 8	Answer 9

Hello, would like some help with this problem. How do I get the factor and freezing pt? This is all that was given, I got the molality of all reagent using the solvent, mass and molecular weight but I do not know hoe to get the Factor and FP. I feel like I have to get the factor first to answer the FP through the formula for vHF=(delta T_f)/{(K_f)(m)}. Is T_f the Freezing Point of Water?

The fromula that I know for delta T is: delta T_f = -iK_fm so I'm kinda stuck

Thank you for the help.

Answer 1

You need to determine how many ions are formed when you dissolve something in a certain solute. So for example, NaCl will dissolve into Na+ ions and Cl- ions. Therefore, the i value would be 2. For ethanol, it would not dissolve in water, so you would just use "1". The concept is, that the freezing point or boiling point is dependent on not just the amount of the solute that is added, but how many "pieces" that is dissolves into.