chem-separating mixtures

1.what techniques could be used to obtain salt from water?
a)crystallization
or
b)distillation

2.why does dye separate during paper chromatography?
a) beacause different colours have different masses
b)beacause different colours have different solubilities <(this might be the answer)
c)beacause different colours are more reactive than others
d)because dye is an insoluble substance

Reply 1

carrotstar

21

Original post by error405

1.what techniques could be used to obtain salt from water?
a)crystallization
or
b)distillation

2.why does dye separate during paper chromatography?
a) beacause different colours have different masses
b)beacause different colours have different solubilities <(this might be the answer)
c)beacause different colours are more reactive than others
d)because dye is an insoluble substance

Crystallisation: NaCl (table salt) is crystalline. In water, it forms a solute (because it is soluble). The aim is to make it precipitate so that it comes out of the water. You can do this either by pushing it out by passing saturation (the maximum solubility), by heating to evaporate the water, or by using another solute which is more soluble in the water than NaCl and which will “push” it out of solution.

All of the above processes are classed as “crystallisation” because they allow the NaCl crystal to form. I hope that helps!

And yes, you are correct with the second question. It is to do with solubility. Essentially different dyes might be more soluble in the solvent (mobile phase) than the paper (stationary phase). How far the molecule travels depends on whether it is more attracted to (has higher affinity to) one or the other.

My explanations are A-level and degree level so I hope I haven’t confused you! But I thought an explanation might help you understand and remember in future.

Reply 2

Estrella_218

16

Original post by error405

1.what techniques could be used to obtain salt from water?
a)crystallization
or
b)distillation

2.why does dye separate during paper chromatography?
a) beacause different colours have different masses
b)beacause different colours have different solubilities <(this might be the answer)
c)beacause different colours are more reactive than others
d)because dye is an insoluble substance

crystallization and b) because different colors have different solubilities