separation of a mixture

[masterspaz]

how do you separate & calculate the percent composition

of potassium chloride and sucrose?

[YT2095]

there`s a few ways you separate them, fractional crystalisation, a solvent to dissolve One of the 2 compounds and then filter, or destroying a compound and leaving the other.

 

for instance you could burn your powder mix so all the sugar is destroyed, then dissolve all this in water and then filter out the carbon, and recrystalise the KCl.

 

weigh the end product and take that from the starting mass, that will give you the Ratio, then you just work that out as a function of 100 to give your Percent.

[masterspaz]

thanks a lot for this info man.

I believe there is another way involving using this reaction:

AgNO3+KCl=AgCl+KNO3

 

so the basic idea is to get the solid part AgCl out and

use stoichiometry to figure out percent composition

 

which one do you think is easier to do?

btw, what is this method i just stated called?

 

 

thanks a lot

[YT2095]

they`re both pretty easy to do, and my method is cheaper

 

yours is a precipitation reaction by Double decomposition.

[John Cuthber]

If you are planning to weigh the AgCl then this is gravimetry*. If you are planning to use a solution of a known concentration and add exactly enough to ppt all the Cl then it's called titration.

 

* Gravimetry is also the word for measuring the local strength of gravity.

[YT2095]

I`de like to see how Titration would work with the silver nitrate reaction!

what indicator do you use to know when it`s complete?

[masterspaz]

for me i just observe, no indicator really, I believe that excess does no harm to the product?

if you have any ways to indicate, either a ratio or any other method, it would be greatly appreciated since AgNO3 isnt the cheapest thing in the world.

[Crooked Mick]

You need a solvent that is selective as YT2095 suggests, I'd suggest ethanol or propanol to begin with, or possibly one of the lower ketones, acetone or methyl ethyl ketone which should dissolve the sucrose and leave MOST of the pot. chloride behind. Someone somewhere has probably tabulated the solubility of each in ethanol or acetone, but I'd guess that pot. chloride is probably slightly slightly soluble in ethanol and acetone. So the separation will not be perfect, but as a first pass with cheap readily available stuff it might not be bad. Supercritical carbon dioxide might also do it but that does not look cheap.

 

Crooked Mick of the Speewah

[John Cuthber]

"I`de like to see how Titration would work with the silver nitrate reaction!"

 

Your wish is my comand.

 

 

Personally I'd use fluorescein as an absorption indicator because it's pretty.

[YT2095]

aha, nice one, as soon as he said dichromate I remembered the red color it makes. cheers

[masterspaz]

im confused, who can explain this in english?

[pioneer]

Crooked Mick and YT2095 had a good suggestion; using a solvant. One needs to use a solvant like a ketone or maybe chloroform. These will extract the sugar and then phase separate into a second layer.

 

Do your density measurement first for the combined solution, then extract the sugar. It may take a few extraction cycles for 95%. Discard this. Boil off the water to see how much KCl. One can then calculate the amout of sugar from the original density and amount of KCl collected.