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Topic: Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)  (Read 9944 times)

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HDC

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Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)
« 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
« Last Edit: September 18, 2005, 01:12:41 PM by Mitch »
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Offline Borek

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Re:Need Help With Chemistry Problem!
« Reply #1 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?
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HDC

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Re:Need Help With Chemistry Problem!
« Reply #2 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
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Offline Borek

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Re:Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)
« Reply #3 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.
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Offline xiankai

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Re:Chemistry Problem: PbCo3.xPb(OH)2 + H2SO4(aq) --> PbSO4(s) + CO2(g) + H2O(l)
« Reply #4 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.
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