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Author Topic: chem question  (Read 9505 times)

Offline Bani

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Re: chem question
« Reply #60 on: October 02, 2009, 04:27:26 pm »
Quote from: nid404 on October 02, 2009, 04:06:50 pm
Z is PbCO3.....so when it is heated it decomposes to form lead oxide and carbon dioxide
yeah u can add reactions...

but they r asking for the molecular formula of Z (PbCO3 is the empirical formula...so what will the molecular formula be?) howcome its CO2 (what happened to the Pb?)
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nid404

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Re: chem question
« Reply #61 on: October 02, 2009, 05:04:14 pm »
they r asking for the molecular formula of Z!! I'm sorry i thought they were asking for the molecular formula of the gas evolved....haste..sorry
okay so

11.2g of PbO would be 11.2/223=0.05 moles....if Z was 0.05 moles....it means their ratio is same...so molecular mass should be PbCO3..

what does the mark scheme say?
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Offline Bani

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Re: chem question
« Reply #62 on: October 02, 2009, 06:07:10 pm »
Quote from: nid404 on October 02, 2009, 05:04:14 pm
they r asking for the molecular formula of Z!! I'm sorry i thought they were asking for the molecular formula of the gas evolved....haste..sorry
okay so

11.2g of PbO would be 11.2/223=0.05 moles....if Z was 0.05 moles....it means their ratio is same...so molecular mass should be PbCO3..

what does the mark scheme say?

hehe no problem
no, i don't have the markscheme. but the method u've shown is what i worked it out as...dunno if its correct...its 3 marks though
« Last Edit: October 02, 2009, 06:38:51 pm by Bani »
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