[Win,odd Dhamnekar]

If Potassium Hydroxide (KOH) weighing 17.64 g was dissolved in 458.1 g water, what is the freezing point and boiing point of the solution?

My answer: Boiling point of the solution is 100.7°C and freezing point of the solution is -2.559°C.

Is this answer correct?   

[Orcio_87]

My answer: freezing point of the solution is 100.7°C and boiling point of the solution is -2.559°C.

Is this answer correct?   

It's wrong as boiling point should be higher than melting point.

But those values are wrong anyway.

[Win,odd Dhamnekar]

Sorry, I made mistake in typing the answer. Now i have corrected my answer. You may check it now.

[Orcio_87]

These values are wrong anyway, it is like changes of temperature were twiced.

[Win,odd Dhamnekar]

Detailed answer:-

First, calculate the 'effective' moles of solute by calculating actual moles and then multiplying by the number of
 'particles' per mole (here we use the symbol 'DF'-dissolving factor for that term).

moles(solute)=DF*mass(solute)/grams formula weight(solute) [itex]\Rightarrow[/itex]2*17.64/56.00=0.6302

Then, after determining the number of kg of solvent, calculate the molality.

kg(H2O)=grams(H2O)/1000 [itex]\Rightarrow[/itex]458.1/1000=0.4581

m=moles(solute)/kg(H2O) [itex]\Rightarrow[/itex]0.6302/0.4581=1.376

The boiling point elevation and freezing point depression are determined by multiplying the molality by the appropriate constants.

ΔT_b=K_b*m [itex]\Rightarrow[/itex] 0.5120*1.376=0.7044
ΔT_f=K_f*m [itex]\Rightarrow[/itex]1.860*1.376=-2.559

Finally, the resultant boiling and freezing points for the solution are calculated using the 'normal' values.

T_b= 100 + ΔT_b 100 +0.7044=100.70

T_f= 0.00 -ΔT_f 0.00 -2.559 =-2.559

[Orcio_87]

Right, values should be twiced due to dissociation (KCl -> K⁺ + Cl^-).

[Borek]

First, calculate the 'effective' moles of solute by calculating actual moles and then multiplying by the number of
 'particles' per mole (here we use the symbol 'DF'-dissolving factor for that term).

No need to reinvent the wheel: https://en.wikipedia.org/wiki/Van_%27t_Hoff_factor