Question

How many grams of BaCl₂ should be added to 300 g H₂O so that the freezing point of the solution is lowered – 8.3 ⁰C ? Assume that the BaCl₂  completely dissociates in the solution.

Answer 1

$\Delta T=ik_cm$

If BaCl₂ is completely dissociated i=3: k for water is 1.86 ^oC/mol m is the molality, i.e the number of moli of salt in 1000 g of water

$m=\frac{ \Delta T}{k_ci}=\frac{8.3}{3x1.8}=1.48$

mole of BaCl₂ is 208 g/ mol you need 92,8 g the croscopy law is true for diluted concentration and this solution isn't and you must use experimental nomogram to solve your problem if you want avoid big mistakes.