Cryometry

Exercise 2

    

What urea mass $CON_2H_4$ should be added to $40\; g$ water to obtain a solution that freezes at $-8^oC$ ?

→   Cryoscopic and ebullioscopic constants

Let be $u$=urea and $e$= water: $\mu_u$ $=$ $\frac{1000\cdot n}{m_e}$ $=$ $\frac{1000\cdot m_u}{M_u\cdot m_e}$ $8$ $=$ $1.86\frac{1000\cdot m_u}{60\cdot 40}$ so: $m_u$ $=$ $10.3\;g$