[blindsided]

Wondering if I did this problem the right way and if I got the right answer.

a.) .800 mole of PbSg : .800mole of PbS/1 X 239g PbS (forumla weight)/1mole PbS = 192.2g PbS

also i have a question about this problem

b.) 4.00 mole of Al2(SO4)3:

would the formula weight be Al+Al+ S+ O^4

or would it be Al+Al+ S^3+ O^12 and I would set it up the same way as a.)?

4 mole of Al(SO)/1 X Forumla weight G Al(SO)/1mole Al(SO)

thanks, i appreciate it


oh, one more.

How many calcium atoms are in 16.2 grams of calcium?

Don't really know what to do for that. so far i have

16.2 Ca X Atoms Ca/ GCa

don't know really where to go with that

[brentr]

b) you are correct in your second explanation... a subscript means multiply everything in the  ( ) by that number.  As for number of molecules I will give you a hint... Use avagadros number, if you need more help let me know.

[Baba]

I think this is how the calculations should be


1. mass(g) =moles x formular weight = .800 x formular weight (molecular weight)


2. this is the correct way to write Al + Al + Sx3 + (Ox3x4)

3. the No of 12g of calcium will have 12gx 6.023 x 10^23 no of calcium atoms
   Where 6.023 x10^23 is the avagadros no.

Please compare with other replies

Cheers
Baba

[Borek]

You were OK up to the 3rd question:

3. the No of 12g of calcium will have 12gx 6.023 x 10^23 no of calcium atoms

You have to convert 12g to number of moles! Avogadro number is number of atoms (molecules...) of substance per MOLE, not per GRAM.