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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: HDC on September 17, 2005, 11:05:03 PM

Title: Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)
Post by: HDC on September 17, 2005, 11:05:03 PM: Hi,

I was wondering if anyone could help me solve the following problem?

A sample of PbCO₃.xPb(OH)₂ was heated with excess sulfurinc acid, yielding PbSO₄(s), H₂O(l), and CO₂(g). If 2.280 g of PbSO₄ and 0.1104g of CO₂ were obtained, what is the value of x?

I've attempted to solve the problem, but I can't seem to have a good grasp of the material. Anyways this is what I've got, thus far:

Chemical Equation: (don't know if it's right or not)
PbCo₃.xPb(OH)₂ + H₂SO₄(aq) --> PbSO4(s) + CO₂(g) + H₂O(l)

I tried converting the values to percentages to see if anything would click as follows:

%PbSO₄ + %CO₂ + %H₂O = 100%
2.280% + 0.1104% + %H₂O = 100%
H₂O = 97.61g H₂O

PbSO₄ = 2.280g PbSO₄
CO₂ = .1104g CO₂
H₂O = 97.61g H₂O

I tried to use the above values to solve for the moles and then for the
Empirical Formula to see if that would give me x but that was no help at all as I got huge mole numbers on one of them. My problem is that, conceptually, I don't know how to proceed.

Can anyone provide a path I should follow to solve this thing?

Thanks,
HDC
Title: Re:Need Help With Chemistry Problem!
Post by: Borek on September 18, 2005, 05:02:45 AM: Quote from: HDC on September 17, 2005, 11:05:03 PM
Chemical Equation: (don't know if it's right or not)
PbCo₃.xPb(OH)₂ + H₂SO₄(aq) --> PbSO4(s) + CO₂(g) + H₂O(l)

Right when it comes to idea, but obviously not balanced. Note that in fact that's two different reactions!

Quote
%PbSO₄ + %CO₂ + %H₂O = 100%
2.280% + 0.1104% + %H₂O = 100%
H₂O = 97.61g H₂O

That's completely wrong approach, no idea what you did, why and what for :(

Hint: start with two different balanced reaction equations. Where did the CO₂ come from?
Title: Re:Need Help With Chemistry Problem!
Post by: HDC on September 18, 2005, 11:44:40 AM: Borek,

I can't visualize the two balanced equations since the problem states that there are three products, "PbSO₄(s) + CO₂(g) + H₂O(l)."
I'm assuming that the CO₂ comes from the PbCO₃.xPb(OH)₂ unless there is something else there I am not seeying.

Anyways, thanks for the help.

HDC
Title: Re:Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)
Post by: Borek on September 18, 2005, 02:55:14 PM: One reactions is PbCO₃ with sulfuric acid, second is Pb(OH)₂ with sulfuric acid. Doesn't matter if carbonate/hydroxide sample is prepared just by mixing two substances, or if they are a unseparated product of some process - there are two different substances and give two different reactions.
Title: Re:Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)
Post by: xiankai on September 18, 2005, 08:23:33 PM: hint : the CO2 can only come from the CO3 and sulfuric acid, while the H2O likewise can only come from the OH- and sulfuric acid.