# - Mole and Avogadro's Number -

1. Nov 19, 2005

### squares

2.95 mol Ba(OH)4 to atoms. (I think I wrote this problem wrong. It might be (OH)2 instead).
I'm confused >.< Do I:
1) multiply 2.95 mol by 6.02 x 10^23 atoms or
or
2) multiply 2.95 mol x 6.02 x 10^23 molcules x 9 atoms.
or is it something else?

Also, how do I do these?
Calculate the mass of 3.01 x 10^23 formula units (ions) of Strontium hydroxide.
Find the number of atoms in 16.0g of sulfur

Last edited: Nov 19, 2005
2. Nov 19, 2005

### eax

moles is amount of particals. When this compound is broken down it is split into 1Ba and 4(OH) [according to you].

moles * 6.02E23= number of particals
(Number of particles)*(Number of particles the molecule can decompose to)=number of ions of that particular particle.

3. Nov 20, 2005

### net_nubie

hence no. of molecules=2.95*6.023*10^23
hence no. of atoms= no. of molecules*no. of atoms per molecule(9 in your case, though it is Ba (OH)2, i.e. 5)
Strontium hydroxide is Sr (OH)2
hence no. of formula units= no. of atoms
hence mass = (molarmass/avogadro's no.)*no. of units
same for next.
refer University Chemistry by Bruce Mahan for details.

4. Nov 20, 2005

### GCT

if they're asking for the atoms of Ba(OH)2 and not its constituent ions, then you would simply solve this by factor labeling

2.95mol Ba(OH)2(6.022x10^23 molecules Ba(OH)2/1mol Ba(OH)2) =?, you should verify that the units cancel out during such processes