A certain substance X has a normal freezing point of -10.1 degree C and a molal freezing point depression constant K_f = 5.32 degree C middot kg middot mol^-1. Calculate the freezing point of a solution made of 29.82 g of urea ((NH_2)_CO) dissolved in 500. g of X. Be sure your answer has the correct number of significant digits.

Respuesta :

Answer: [tex]-15.4^00C[/tex]

Explanation:

[tex]T^0_f-T_f=i\times k_f\times \frac{w_2\times 1000}{M_2\times w_1}[/tex]

where,

[tex]T_f[/tex] = boiling point of solution = ?

[tex]T^o_f[/tex] = boiling point of solvent (X) = [tex]-10.1^oC[/tex]

[tex]k_f[/tex] = freezing point constant  = [tex]5.32^oC/kgmol[/tex]

m = molality

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

= mass of solute (urea) = 29.82 g

= mass of solvent (X) = 500.0 g

[tex]M_2[/tex] = molar mass of solute (urea) = 60 g/mol

Now put all the given values in the above formula, we get:

[tex](-10.1-(T_f))^oC=1\times (5.32^oC/m)\times \frac{(29.82g)\times 1000}{60\times (500.0g)}[/tex]

[tex]T_f=-15.4^0C[/tex]

Therefore, the freezing point of  solution is [tex]-15.4^0C[/tex]