Grade 12Physical Chemistry

Which of the following aqueous solutions will have the lowest freezing point??

A.) 0.1 M KCl

B.) 0.1 M Al2(SO4)3

C.) 0.1 M C6div2O6

D.) 0.1 M C12 H22 O11

...PLS ANSWER DIS WITH EXPLANATION... N ALSO HOW TO FIND IF QUESTION IS BOILING POINT INSTEAD OF FREEZING POINT????

raghasri raghavan

12 Years agoGrade 12

4 Answers

Kamlesh Kumar

12 Years ago

colligative properties like depression in freezing point and elevation in boiling point directly depends over no. of particles of solute.but freezing point &boiling point are not colligative properties.so in this question lowest freezing point is of 0.1 M Al₂(SO₄)₃due to greater no. of particles & hence greater deppression in freezing point takes place.and in case of boiling point ,value of boiling point will be lowest for 0.1 M C₁₂H₂₂O₁₁due to elevation in b.p will be lowest for 0.1 M C₁₂H₂₂O_11.

thanks&regards

kamlesh kumar

askiitians faculty

raghasri raghavan

12 Years ago

sir bt how that has more no. of particles????

ruthwik

8 Years ago

hello

we can know how many particals are there by caliculating

the mass of the compound the more mass the more particles

Kushagra Madhukar

5 Years ago

Dear student,

Please find the answer to your question below.

We know that the depression in freezing point, ΔT_f = i x K_f x m

Now, all the options are aqueous solution, Hence value of K_f is same for all.

Also molality, m is almost the same for all

Hence it predominantly depends on van’t hoff factor, i

Since i is maximum for Al₂(SO₄)₃ [i = 5]

Hence Al₂(SO₄)₃ has the highest depression in FP or the lowest Freezing Point in the given options.

If Boiling point was asked the sequence would be reversed, as we observe elevation in case of boiling point, due to which the lesser the value of i, the lesser will be the Boiling Point.

But in the given option there are two compounds glucose and sucrose with i = 1.

Hence, here the molality comes into picture.

Both Glucose and sucrose have the same molarity (0.1 M), but as Sucrose has higher molar mass, it will also have higher molality compared to glucose.
Hence, the elevation in Boiling point will be slightly higher for Sucrose than Glucose.

Hence, when Boiling point will be asked, Glucose(C₆H₁₂O₆) will have lowest Boiling point.

Thanks and regards,

Kushagra