Question

Consider 0.1 M aqueous solutions of NaCl(aq), CaCl2(aq), HCl(aq), HF(aq), NH3(aq), and table sugar(aq),

a. Identify each of the above as strong, weak, or non electrolytes.

b. Of the above solutions, which should conduct electricity the best? The worst? c. Rank the above solutions from lowest vapor pressure (25˚C) to highest vapor pressure.

d. Rank the above solutions from lowest boiling point (1 atm) to highest boiling point.

e. Which solution should have the lowest melting point?

g. Which of the above compounds are ionic? Which are molecular?

Answer 1

Consider 0.1 M aqueous solutions of NaCl(aq), CaCl2(aq), HCl(aq), HF(aq), NH3(aq), and table sugar(aq),

Solution :- We are given with the same concentration solutions but the colligaive properties of the solution depends on the total ion or total particle concentration of the solution.

So total ion concentration of the NaCl = 0.1 M * 2 = 0.2 M

CaCl2 = 0.1 M *3 = 0.3 M

HCl =0.1 M *2 = 0.2 M

HF and NH3 are weak acid and base therefore they do not dissociate 100 % so we can consider there concentration as 0.1 M

Sugar is the non electrolyte so its total concentration is also 0.1 M

a)Identify each of the above as strong, weak, or non electrolytes.

Solution :-

Strong electrolytes means the compounds which dissociate 100 % to form ions

And weak electrolytes means the compounds which dissociates partially

Non electrolytes do not dissociate.

So classification is as follows

Strong electrolytes = NaCl ,CaCl2, HCl

Weak electrolytes = HF and NH3

Non electrolyte = sugar

b) Of the above solutions, which should conduct electricity the best? The worst? c. Rank the above solutions from lowest vapor pressure (25˚C) to highest vapor pressure.

Solution :- NaCl , CaCl2 and HCl would conduct electricity best because they are strong electrolytes.

And sugar solution is the worst conductor of electricity.

Rnaking based on the vapour pressure lowest to highest.

CaCl2 < HCl<NaCl<HF < NH3<sugar

d. Rank the above solutions from lowest boiling point (1 atm) to highest boiling point.

Solution :- lower concentration means lowest boiling point and higher concentration means higher boiling point

CaCl2 > NaCl> HCl > HF>NH3> sugar

e. Which solution should have the lowest melting point?

Solution :- CaCl2 solution would have lowest melting point because its concentration of total ion would be higher.

g. Which of the above compounds are ionic? Which are molecular?

Solution : -CaCl2 and NaCl are ionic compounds.

(Because thy have metal and non-metal element bond.)