Hard Chemistry Question (1 Viewer)

[axwe7]

I am a Year 11 student, in Chemistry I've only started the module known as; "The Chemical Earth".

QUESTION:

2g of each of the following pars of solids are mixed. Could they be successfully separated by filtration techniques? The solubility of each substance in 1 Litre of water is given in brackets

(a) Potassium Sulfate (120g/L) / Lead Iodide (0.8g/L)
(b) Magnesium Carbonate (0.6g/L) / Silver Oxide (0.02g/L)

Sorry if it isn't hard for you, but for a student who has not yet learnt the solubility rules table, it considerably is.

Thanks.

 

[Drsoccerball]

I am a Year 11 student, in Chemistry I've only started the module known as; "The Chemical Earth".

QUESTION:

2g of each of the following pars of solids are mixed. Could they be successfully separated by filtration techniques? The solubility of each substance in 1 Litre of water is given in brackets

(a) Potassium Sulfate (120g/L) / Lead Iodide (0.8g/L)
(b) Magnesium Carbonate (0.6g/L) / Silver Oxide (0.02g/L)

Sorry if it isn't hard for you, but for a student who has not yet learnt the solubility rules table, it considerably is.

Thanks.

From my crap knowledge of chem so may be wrong...
(a) Potassium isn't soluble in Iodide but Lead is soluble with Sulfate so you can't separate Lead and Sulfate but you can separate Potassium and Iodide.
(b) Silver and carbonate are soluble so you can't separate them and also with Magnesium and OXide.

 

[axwe7]

From my crap knowledge of chem so may be wrong...
(a) Potassium isn't soluble in Iodide but Lead is soluble with Sulfate so you can't separate Lead and Sulfate but you can separate Potassium and Iodide.
(b) Silver and carbonate are soluble so you can't separate them and also with Magnesium and OXide.

Yes, of course it works with the solubility table, however, take into account that this is a question from "The Chemical Earth" module. Hence how could you answer the question?

 

[Drsoccerball]

Yes, of course it works with the solubility table, however, take into account that this is a question from "The Chemical Earth" module. Hence how could you answer the question?

No there's no other way to answer this except through solubility rules as they describe if things can physically be separated.

 

[eyeseeyou]

Are you sure this is from the chemical earth? Doesn't seem like it

 

[leehuan]

This is very much the chemical Earth thanks.
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In case a), we note that up to 120g of K2SO4 can be dissolved in 1L of water. If we only have a mere 2g of K2SO4 then all of it will dissolve.

Whereas only 0.8g of PbI2 will dissolve. Because we have 2g of PbI2, not all of that is going to dissolve.

Hence, PbI2 can be seperated by filtration. The PbI2 will be the filtrate.

If we slowly evaporate off the water to 500mL, then only 0.4g of PbI2 will be dissolved and another 0.4g will be precipitated. We can thus use filtration again.

This process continues until we essentially extract out as much PbI2 as possible. Once we only have one-sixtieth of a litre, we will start precipitating K2SO4 instead. But at that point, the amount of PbI2 present is so negligible that we can evaporate off all the water and collect the K2SO4.
___________________
Whereas in case b), initially both substances will be dissolved. Thus, there is no IMMEDIATE way to proceed with separating the two substances. We would have to evaporate off water straight away to collect any substance.
___________________
What I WON'T deny, is that this question has substantial difficulty involved.

 

[axwe7]

This is very much the chemical Earth thanks.
__________
In case a), we note that up to 120g of K2SO4 can be dissolved in 1L of water. If we only have a mere 2g of K2SO4 then all of it will dissolve.

Whereas only 0.8g of PbI2 will dissolve. Because we have 2g of PbI2, not all of that is going to dissolve.

Hence, PbI2 can be seperated by filtration. The PbI2 will be the filtrate.

If we slowly evaporate off the water to 500mL, then only 0.4g of PbI2 will be dissolved and another 0.4g will be precipitated. We can thus use filtration again.

This process continues until we essentially extract out as much PbI2 as possible. Once we only have one-sixtieth of a litre, we will start precipitating K2SO4 instead. But at that point, the amount of PbI2 present is so negligible that we can evaporate off all the water and collect the K2SO4.
___________________
Whereas in case b), initially both substances will be dissolved. Thus, there is no IMMEDIATE way to proceed with separating the two substances. We would have to evaporate off water straight away to collect any substance.
___________________
What I WON'T deny, is that this question has substantial difficulty involved.

That's more like it

Thanks Leehuan, you have once again proved to me your great services, you are now dismissed from this post.