Answer to Question #254733 in General Chemistry for Kath

Question

Find the molar mass of a juice drink that contains 1000 mg of Vitamin C in 757 g of water. The change in freezing point depression is 0.014 ⁰C.  Kf = 1.86 °C/m       

 

Answer 1

The freezing point depression:

$∆T = k_f \times c_m$

k_f = the molal freezing point depression constant

c_m = the molality of the solute

$k_f = 1.86 \\ c_m = \frac{n}{m_{water}} = \frac{\frac{m}{M}}{m_{water}} \\ 0.014 = 1.86 \times \frac{\frac{1 \;g}{M}}{0.757 \;kg} \\ 0.014 = \frac{1.408}{M} \\ M = 100.57 \;g/mol$