## anonymous 4 years ago You have 20g of cobalt. How many atoms of cobalt is this?

1. Xishem

This is similar to the other question you asked. First convert from grams of Co to mols of Co, and then from mols of Co to atoms of Co using the knowledge that there are 6.022*10^23 of something in 1mol of something.

2. anonymous

I got 5.65x10^21 atoms

3. Xishem

Well, let's see... $20g(Co)*\frac{1mol(Co)}{58.933g(Co)}=0.33937mol(Co)$$0.33937mol(Co)*\frac{6.022*10^{23}atoms(Co)}{1mol(Co)}=2.0437atoms(Co)=2.0*10^{23}atoms(Co)$Do you see where you made your mistake?

4. Xishem

In the second set of equations, it should be...$2.0437*10^{23}atoms(Co)=2.0*10^{23}atoms(Co)$

5. Xishem

Just remember to always make sure that your units make sense. If you follow your units, 90% of the time (especially in entry-level chemistry), you will be lead in the correct direction.