chemistry organic help please.....

Question

The freezing point of equimolal  aqueous solution will be highest for ?

1. C6H12O6 (GLUCOSE)

2. La(NO3)₃ 

3. Ca(NO3)₃ 

4. C6H5NH3Cl (ANILINE HYDROCHLORIDE)  

    

=>  i  want to know for this question  do i really need to know the freezing point  values of each of the options to attempt this one  or there are other factors that could help me to find the answer for this without knowing  values ?

Answer 1

Colligative properties, such as depression of FP, depend on the total number of particles present. Ionic compounds dissociate into their component ions. Non-ionic (covalent) compounds don't dissociate.

 

So #1 is organic (covalent) and has no ions. 

    #2 and #3 will both dissociate into 4 ions per formula, or 4 moles of ions per mole of compound. 

     #4 will dissociate into 2 ions per formula (rather like ammonium chloride dissociates into NH_{4 ⁺}  and Cl^_ ).

 

Since the solutions are equimolar, the one with the highest FP is the one with the smallest FP depression, which is the one with fewest ions.

 

The answer is #1. Glucose solution still freezes lower than pure water, but not as low as the other solutions.