Qualification > Sciences
chem question
nid404:
Pb C O
% 77.5 4.5 18
Mass 207.2 12 16
moles 77/207.2 4.5/12 18/16
=0.3716 =0.375 =1.125
ratio 1 1 3
empirical--PbCO3
you're right ;)
nid404:
Third one
molecular formula is CO2.....it's very obvious....
what confusion did u have in this one....easiest of the lot
Bani:
--- Quote from: nid404 on October 02, 2009, 06:10:38 am ---b) Combine the reactions
2PbS + 3O2 ----> 2PbO + 2SO2
2PbO + PbS ----> 3Pb + SO2
you get
3PbS+3O2--->3Pb+3SO2
ratio of sulphide to sulphur dioxide is 1:1
mass in 1 mole of lead sulphide=239.265
mass of lead sulphide used= 5x10^3 X1000g=5X10^6g
moles of lead sulphide=5x10^6/239.265
=20897.33moles
volume of sulphur dioxide=moles X 2.4X10^-2 =501.53 m3
--- End quote ---
Thank-you.....is it ok to combine the 2 reactions?...cuz my teacher never told us we can do that. oh and y do u use 239.265 for the mol.mass? y not (207+32=239) ?
Bani:
--- Quote from: nid404 on October 02, 2009, 06:18:39 am ---Third one
molecular formula is CO2.....it's very obvious....
what confusion did u have in this one....easiest of the lot
--- End quote ---
isn't compound Z also suppossed to have lead in it? (Pb, C and O) so..how wud we work out the molecular formula? nd in the Q. it tells us the mass of lead(II) oxide (11.2g)
nid404:
Z is PbCO3.....so when it is heated it decomposes to form lead oxide and carbon dioxide
yeah u can add reactions...
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