Liquid solutions

1. Aug 27, 2017

Tanishq Nandan

1. The problem statement, all variables and given/known data
A solution contains 0.1mol of acetamide in 1Lit of glacial acetic acid.When the solution is cooled,the first crystal that appeared at the freezing point contains the molecules of
A.acetamide only
B.Acetic acid only
C.both acetamide and acetic acid
D.None
2. Relevant equations
Depression in freezing point=(molal depression constant)*(molality of solution)

3. The attempt at a solution
I don't see why there should be anything other than C.
It's a solution..consists of both solute and solvent,which have formed a composite mixture that freezes at the same temperature.So,shouldn't the crystal contain both of those components.
However,answer given is B

2. Aug 27, 2017

Staff: Mentor

That would be an eutectic system, not every mixture works this way.

3. Aug 27, 2017

Tanishq Nandan

Oo..well,then how can we predict the answer for this question?

4. Aug 27, 2017

Staff: Mentor

Just by looking at the melting points.

5. Aug 28, 2017

Tanishq Nandan

But..that isn't given in the question...and I don't think I'm supposed to remember the melting pt of either acetamide or acetic acid..

6. Aug 28, 2017

Staff: Mentor

On the second thought - melting point would be the most important thing for mixture in which molar fractions of both substances involved are comparable. When concentration of the solute is much lower, its activity is also very low, so it can not freeze that easily.

I don't like the question, I am not convinced the answer is easy to give without additional information.

7. Aug 28, 2017

Ok,thank you