You are a physician in an emergency ward. A girl has entered respiratory collapse due to chewing on wood covered with a lead-based paint. Tests have shown [ce]PB^2+[/ce] in her blood to be 1.5 x 10^-5 mol/L. Reports have shown that [Pb] > 1.0 x 10^-9 can be considered lethal. To quickly reduce [Pb] to 1.0 x 10^-9 mol/L you have decided to inject a [ce]Na2CO3[/ce] solution directly into her blood so as to cause a [ce]PBCO3[/ce] precipitate to form [ce]K_sp = 3.3 x 10^-14)[/ce], which can be filtered from the blood by her kidneys. If her body contains 1.7L of blood, what mass of [ce]Na2CO3[/ce] is required to precipitate the Pb from her blood and bring [Pb^2+] down to 1.0 x 10^-9 mol/L. Since [ce]Na2CO3[/ce] is lethal in large amounts you must not administer an overdose!!

 

So figure it yourself, and post your answer. I'll figure it out myself first, then we can discuss more later.

Heh. So we'll ignore the fact that the precipitate would wind up blocking the arteries and veins in her brain and vital organs and kill her instantly?

You misunderstood for 3 reasons:

(1)The solution is being injected - meaning the solution is in a needle and being put in the arm or something like that.

(2)The precipitate will form inside her body, not in the mouth!!

(3)It won't be too much precipitate enough to kill her.

 

So jdurg the Chemistry Expert.. Do you have an answer for my question yet??

Ok this is likely to be wrong but i got 0.0027 grams of PbCO3, although i have a feeling that may kill her lol

[Pb2+] = 1.5 x 10-5 mol dm-3

 

[Pb2+] > 1.0 x 10-9 is lethal

 

Ksp of PbCO3 = 3.3 x 10-14

 

Volume of blood = 1.7 dm3

 

~~~~~~~~~~PbCO3~~~~>> ~~~~~Pb2+ ~~~~+~~~CO32-

Initial~~~~~~1.5 x 10~~~~~~~~~~~~y~~~~~~~~~~~ -

Changes~~–(1.4999 x 10-5 )~~~–(1.4999 x 10-5 )~~~+(1.4999 x 10-5 )

Equilibrium~~~1.0 x 10-9~~~~ y –(1.4999 x 10-5 )

 

 

Ksp = [Pb2+][ CO32-]

 

(1.0 x 10-9 ) (y –1.4999 x 10-5 ) = 3.3 x 10-14

 

y = 4.7999 x 10-5

 

no of mole of Na2CO3 = 4.7999 x 10-5

volume of blood

 

Mass of Na2CO3 /106 = 4.7999 x 10-5

1.7

 

Mass = 8.65 x 10-3 g

 

 

Is this correct ?

I am wondering how kidney is able to filter out the precipitate?

Heh. So we'll ignore the fact that the precipitate would wind up blocking the arteries and veins in her brain and vital organs and kill her instantly?

- Jdurg

 

You misunderstood for 3 reasons:

(1)The solution is being injected - meaning the solution is in a needle and being put in the arm or something like that.

(2)The precipitate will form inside her body, not in the mouth!!

(3)It won't be too much precipitate enough to kill her.

-Evo

 

1. Jdurg probably knew that(if he didn't i'll eat my hat)

2. where the hell did Jdurg say it formed in her mouth. the precipitate would form in the arteries and veins which would then cause blockages and strokes in the brain.

3. it probably would be.

Ok this is likely to be wrong but i got 0.0027 grams of PbCO3, although i have a feeling that may kill her lol

 

The question requested for the mass of [ce]Na2CO3[/ce] not [ce]PbCO3[/ce].

[Pb2+] = 1.5 x 10-5 mol dm-3

 

[Pb2+] > 1.0 x 10-9 is lethal

 

Ksp of PbCO3 = 3.3 x 10-14

 

Volume of blood = 1.7 dm3

 

~~~~~~~~~~PbCO3~~~~>> ~~~~~Pb2+ ~~~~+~~~CO32-

Initial~~~~~~1.5 x 10~~~~~~~~~~~~y~~~~~~~~~~~ -

Changes~~–(1.4999 x 10-5 )~~~–(1.4999 x 10-5 )~~~+(1.4999 x 10-5 )

Equilibrium~~~1.0 x 10-9~~~~ y –(1.4999 x 10-5 )

 

 

Ksp = [Pb2+][ CO32-]

 

(1.0 x 10-9 ) (y –1.4999 x 10-5 ) = 3.3 x 10-14

 

y = 4.7999 x 10-5

 

no of mole of Na2CO3 = 4.7999 x 10-5

volume of blood

 

Mass of Na2CO3 /106 = 4.7999 x 10-5

1.7

 

Mass = 8.65 x 10-3 g

 

 

Is this correct ?

 

You are using the ICE method' date=' very good. But you have an error in your calculation, because you know that the "change" for [ce']PbCO3[/ce] is -1.4999 x 10^5, therefore it should be positive over the other side. Your reply was –(1.4999 x 10-5 ). It should be positive. Also, please use "^" for exponents. I don't want to get confused. Secondly, what does "dm3" means?

It stands for Dm^3

ie Decimeter Cubed

So Litre (L) is same as Dm^3?

Well, yes.

 

A decimeter cubed is (10cm)^3 and therefore 1000cm^3, which is a litre!

I disagree with you, because 1 L equals to 1,000 mL. But perhaps you are speaking of volume?

Yeah, 1000mL is 1000cm^3

 

So basically, 1000mL=1000cm^3=1 litre

 

Basically speaking, they are three different ways of speaking about the same thing! Thats science for you

Thanks. Now can anybody answer my chemistry question from post #1??

PbCO3 would precipitate in the blood and the girl would die

This looks a lot like someone's homework.

This looks a lot like someone's homework.

 

I don't know about that. The question itself is kind of laughable at best, because you wouldn't inject a carbonate into anybody's blood to purposely ppt out a heavy metal. That would lead to a ppt forming in a critical capillary in various organs and result in almost certain death. In addition, the alkalinity of the carbonate ion could cause other problems. EDTA is typically used in a metal poisoning becuase it does bind with the heavy metal, but at the same time remains soluble in the blood so as not to cause blood vessel blockages.

This looks a lot like someone's homework.

 

Agreed

 

and I think the idea is to strip away the trivial data and boil it down to the equasion part, how much X is needed to "neutralise" Y. and not get caught up in malpractice suits

 

Jdurg, Yeah EDTA and activated charcoal are the typical A&E procs

EDTA calculations of this sort are so simple. 1:1 stoichiometry

Seems like nobody here can answer my question

once again, PbCO3 would precipitate in the blood and the girl would die

[Pb2+] = 1.5 x 10-5 mol dm-3

 

[Pb2+] > 1.0 x 10-9 is lethal

 

Ksp of PbCO3 = 3.3 x 10-14

 

Volume of blood = 1.7 dm3

 

~~~~~~~~~~PbCO3~~~~>> ~~~~~Pb2+ ~~~~+~~~CO32-

Initial~~~~~~1.5 x 10~~~~~~~~~~~~y~~~~~~~~~~~ -

Changes~~–(1.4999 x 10-5 )~~~–(1.4999 x 10-5 )~~~+(1.4999 x 10-5 )

Equilibrium~~~1.0 x 10-9~~~~ y –(1.4999 x 10-5 )

 

 

Ksp = [Pb2+][ CO32-]

 

(1.0 x 10-9 ) (y –1.4999 x 10-5 ) = 3.3 x 10-14

 

y = 4.7999 x 10-5

 

no of mole of Na2CO3 = 4.7999 x 10-5

volume of blood

 

Mass of Na2CO3 /106 = 4.7999 x 10-5

1.7

 

Mass = 8.65 x 10-3 g

 

 

Is this correct ?

 

I must quite frankly apologize to builgate because he got the correct answer. Congratulations builgate!! The answer I got was [math]8.6 x 10^-3 g[/math] after I figured it out. My method is a little different than what he did, so I will post my method for you guys tomorrow. (I promise it will be very clear). I don't have the time right now as I need to study for 2 Advanced Unit tests tomorrow, so wish me good luck!

 

Heh. So we'll ignore the fact that the precipitate would wind up blocking the arteries and veins in her brain and vital organs and kill her instantly?

yeah i had a feeling that would happen