[PrincessJenny]

I need help figuring this out please..

find the number of atoms in

a) 52.5 g of calcium metal

b)  1.5 mol of carbon

c)  15 mol of carbon dioxide

[Mitch]

Read the following http://www.chemicalforums.com/index.php?page=forumrules

[kimi85]

from grams you can convert it to moles, then to the number of atoms.
1 mole = 6.02 x 10 raised to 23 atoms

[03myersd]

Wooo! First post!!! Anyway....

If I show you (what i think is the right way) how to do the first question you can then figure out the others from this.


Ca has 40g per mole. (gotten from the atomic mass of 40amu)

then we know that in this one mole of calcium there are 6.022x10^23 atoms. This is a constant number known as Avogadro's number.

To get how many atoms are in 52.5g or calcium we have to find the correct ratio. We do this by dividing 52.5 by 40. Giving us 1.3125.

Then its simple a case of multiplying 6.022x10^23 by 1.3125 which gives us the grand total of....

7.904x10^23 atoms.


This was only my first post so I hope everything is ok with it. And sorry if I have given a wrong solution.

[omfgwtfcamelbbq]

I need help figuring this out please..

find the number of atoms in

a) 52.5 g of calcium metal

b)  1.5 mol of carbon

c)  15 mol of carbon dioxide

To do this remember

1 mol=relative atomic mass of element/compound.
1 mol=6.02*10^23 particles

therefore

--------------------------------------------------------------------------------

mass of calcium/relative atomic mass = # of moles

--> 52.5/40.08 = 1.30988024 mol of calcium atoms

6.02*10^23 particles (atoms in this case) per mol

-->1.30988024*6.02*10^23 = 7.885479042*10^23

----->7.885479042*10^23 atoms of calcium in 52.5g of calcium metal

---------------------------------------------------------------------------------

6.02*10^23 particles (atoms) per mol
# of mol * 6.02*10^23

-->1.5*6.02*10^23 = 9.03*10^23
----->9.03*10^23 atoms in 1.5 mol or carbon
----------------------------------------------------------------------------------

6.02*10^23 particles(atoms) per mol
# of mol of molecule * # of atoms in each molecule * 6.02*10^23

-->15*3*6.02*10^23 = 2.709*10^23
----->2.709*10^23 atoms in 15 mol of CO2
----------------------------------------------------------------------------------

Hope thats right...

Jacob

[PrincessJenny]

Thank-you everybody!!!! esp. for explaining it in steps..   
i really appreciate it.. this was my first post to this site.  I'm taking this chemistry course through correspondence.

[whitelotus1983]

are you done with your ILC yet?

[legking]

I'm taking the same course. Thanks for this!

[Epidii Heiress]

Wow, lots of ILC students on this forum, eh?

I know this is an old question, but since it was already posted, I thought I would just append my question to this one instead of starting a new thread.

Question c) should actually be:
Find the atoms in 1.5 mol of carbon dioxide.

I understand the principle behind finding the number of atoms... no problem there, but how does dealing with a compound like CO₂ affect the formula?

If 1.5 mol of carbon = 9.0 x 10²³ atoms, is the answer for 1.5 mol of carbon dioxide the same (since the number of mols is the same?) 

Thanks, and sorry for beating a dead horse.  First time poster.   

[Borek]

If 1.5 mol of carbon = 9.0 x 10²³ atoms, is the answer for 1.5 mol of carbon dioxide the same (since the number of mols is the same?)

OK for carbon. How many atoms of oxygen?

[Epidii Heiress]

N/M, I think I figured it out.  

There are 2 oxygen atoms, so I solve again for 1.5 moles of oxygen and multiply it by two, then add it to the number of atoms for carbon?  My final answer was 2.71 x 10²⁴ atoms.

[Borek]

Looks OK