Question

What mass of glucose (C6H12O6) should be dissolved in 12.0 kg of water to obtain a solution with a freezing point of -5.8 ∘C?

Answer 1

Mass of glucose : 6.7356 kg

Further explanation  

Solution properties are the properties of a solution that don't depend on the type of solute but only on the concentration of the solute.  

Solutions from volatile substances have a higher boiling point and lower freezing points than the solvent  

For freezing point can be formulated

$\tt \Delta T_f=K_f.m$  

K = molal freezing point constant  

m = molal solution  

A solution with a freezing point of -5.8 ∘C

$\tt \Delta T_f=T_f~solvent-T_f~solution=0-(-5.8)=5.8$

$\tt mass~of~glucose:\\\\\Delta T_f=K_f.m\\\\5.8=1.86^oC/m.\times \dfrac{mol~glucose}{12}\\\\mol~glucose=\dfrac{5.8\times 12}{1.86}=37.42$

$\tt mass=mol\times MW=37.42\times 180=6735.6~g=6.7356~kg$