Chemistry??

Question

If a solution were to change its composition during freezing how do you think this would change the cooling curve?

What is the relationship between the amount of solute and the amount of freezing point depression?

Do you think all solutes would behave basically the same? What factors might make solutes differ?

What is the mass of 0.005 moles of camphor, urea, and potassium ethanoate?

Can any one answer any of these???

Answer 1

1) If a solution change it's composition - that's a hard question to answer - because I don't know what you are referring to. Does the solution add acid? - well if so - the cooling curve is going to be quite different than if say, you added 10 drops of satd, NaCl solution! or lump of Na metal?!

2) The more of a substance you add (up to a certain limit) will continue to increase your freezing point drepression.

3) No. All solutes do not behave to same. Solutes are effected by the solvents they are in, and also to their OWN chemical make up. Also, some materials as solutes can be reactive in solution and stable in solid form.

4) 0.005 mole of
Camphor 152.23 g/mole =0.761 g
Urea 60.07 g/mole = 0.300 g
KOOCH3 98.25g/mole = 0.491 g

Answer 2

Dr Dave P answered the last question ably.

If the solution changes composition by crystallization of pure solvent, thus concentrating the solution that's left, then the cooling curve will end up at a lower temperature than "normal."

If the solution changes because solute drops out of solution, leading to dilution of the remaining solution, then the cooling curve will finish higher.

The greater the concentration of siolute, the greater the freezing point depression.

Solutes could differ by ionization. CaCl2 gives three moles of ions per mole of salt, which makes it great for depressing the freezing point of water on driveways in winter. Potassium ethanoate (acetate) gives two ions per mole. Camphor and urea do not ionize.

Answer 3

In change,the energy must be take into account.The relation may be linear for a small variation.Not all may behave the same.The amount of energy and the probability for change.The mass may be obtained easy,knowing the formula.