In this video you are going to learn how
to convert particles, atoms, molecules, and
formula units, all to moles using
Avogadro's number. Alright, let's do this.
Avocado? No, no it's Avogadro.
Hello hello Melissa Maribel here and I help students like you understand what you just
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chemistry together.
Avogadro's number is yet again another
conversion factor which allows you to go
from particles, atoms, molecules, and
formula units, all to moles. Avogadro's
number specifically is 6.022x10^23.
That number goes with particles,
atoms, molecules, and formula units and it
all equals one mole.
Here's a tip for you, whenever you see
the words particles, atoms, molecules, or
formula units, that is your clue to use
Avogadro's number as a conversion factor.
Why don't we head over to the laughaboratory
for a way to remember Avogadro's number.
Here's a way to remember that one mole
is equal to Avogadro's number. You can't
have the guacamole
without the avocado.
(Crowd boo's) Can I have some chips at least?
On to the examples. How many atoms are
in 1.5 moles of CO2 or carbon dioxide. As
always identify your given and what
you're finding. Our given is 1.5 moles of
CO2. We're finding atoms of CO2. So your
plan is just going from moles to atoms.
Keyword atoms, so we know we're going to
use Avogadro's number as our conversion
factor. Always starting with your given
on top, aligning your units across so
they can cancel and we'll place Avogadro's number on top to get that atoms.
Multiply straight across and you get
9.033 x 10^23
atoms of CO2, but we have to round
because our sig figs tell us from our
given there's only two sig figs. Rounding
to two sig figs you get 9.0 x 10^23 atoms of CO2.
The
next example goes from formula units
to moles. How many moles are in 7.2x10^10 formula units of NaCl or
sodium chloride? As always figuring out
what you're given and what you're
finding. So we're given the 7.2x10^10 formula units
and we're just going to moles of NaCl.
Your plan is going from your given unit
of formula units to moles. Key word here,
formula units. We know we're using
Avogadro's number as our conversion
factor. Your setup, starting with your
given on top, aligning those units across
from each other so they can cancel and
this time Avogadro's number is on the
bottom just so we can cancel out those
formula units. Divide these two numbers
and you get, 1.1956x10^-13 moles
but we have to round up since our
sig figs are only two sig figs from the
given.
Our answer then is 1.2 x 10^-13 moles of NaCl. You ready to try it on your own?
I've linked up practice problems in the
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