At -18.6 °C, a common temperature for household freezers, what is the maximum mass of sucralose (C₁₂H₁₉Cl₃O₈) in grams you can add to 2.00 kg of pure water and still have the solution freeze?
Assume that sucralose is a molecular solid and does not ionize when it dissolves in water.
[tex]K_f[/tex] = 1.86 °C/m.

Answer :

Answer : The maximum mass of sucralose is, 7952.8 grams.

Explanation :  Given,

Molal-freezing-point-depression constant [tex](K_f)[/tex] for water = [tex]1.86^oC/m[/tex]

Mass of water (solvent) = 2.00 kg

Molar mass of sucralose = 397.64 g/mole

Formula used :  

[tex]\Delta T_f=i\times K_f\times m\\\\T^o-T_s=i\times K_f\times\frac{\text{Mass of sucralose}}{\text{Molar mass of sucralose}\times \text{Mass of water in Kg}}[/tex]

where,

[tex]\Delta T_f[/tex] = change in freezing point

[tex]\Delta T_s[/tex] = freezing point of solution = [tex]-18.6^oC[/tex]

[tex]\Delta T^o[/tex] = freezing point of water = [tex]0^oC[/tex]

i = Van't Hoff factor = 1 (for sucralose non-electrolyte)

[tex]K_f[/tex] = freezing point constant for water = [tex]1.86^oC/m[/tex]

m = molality

Now put all the given values in this formula, we get

[tex](0-(-18.6)^oC)=1\times (1.86^oC/m)\times \frac{\text{Mass of sucralose}}{397.64g/mol\times 2.00kg}[/tex]

[tex]\text{Mass of sucralose}=7952.8g[/tex]

Therefore, the maximum mass of sucralose is, 7952.8 grams.

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