Converting from Particles to Mass and Mass to Particles

So now that we understand how to convert from grams to moles, moles to grams, particles to moles and moles to particles, let's try converting from particles to grams and grams to particles.

These are now 2 step conversions. Once again we need our periodic table.

Let's start with particles to mass.

If you have 2.78 x 10^22 Fe atoms, how many grams are there?
First, you want to get rid of the atoms, so let's go from atoms to moles.

2.78 x 10^22 atoms of Fe x 1 mole / 6.022 x 10^23 atoms

Now, we also know how to go from moles to grams, so let's get rid of moles.

2.78 x 10^22 atoms of Fe x 1 mole / 6.022 x 10^23 atoms x 55.8g (molar mass of Fe) / 1 mole

Now our final answer is going to be (2.78 x 10^22)(55.8g) / (6.022 x 10^23) in 3 sig figs.
So, we get 2.58g. This means 2.78 x 10^22 Fe atoms weighs 2.58 g.

Now mass to particles...How many atoms of Fe are in 20.0g of Fe?
So, we get rid of grams by multiplying moles/grams.

20.0g of Fe x 1 mole / 55.8g (molar mass of Fe)

Then, since we want particles, we get rid of moles by multiplying particles/moles.

20.0g of Fe x 1 mole / 55.8g (molar mass of Fe) x 6.022 x 10^23 atoms / 1 mole
Our final answer of 20.0g Fe in particles (3 sig figs) is 2.16 x 10^23 atoms.

Video time :)