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Chemistry is about out the atomic mass of carbon is
Measuring 12, and the atomic mass for
oxygen is 16. Here’s how you find
So many chemistry courses skip
the mass of CO 2:
this vital step, and it’s essential if
C + 2 (O) 12 + 2(16) = 44
you want to master chemistry lab
skills. You must learn how to So one mole of CO 2 weighs 44
measure if you’re going to make grams. This now becomes our
any headway in doing chemistry. conversion factor of (1 mole)/(44
grams) and we use it like this:
Moles A mole is a unit of
measurement, just like inches or Number of moles of CO 2 = 500g x
meters. Since chemical reactions (1 mole/44grams) = 11.4 moles
take place on such a small scale,
So there are 11.4 moles of CO 2 in
the unit of the mole was invented
500 grams.
to help keep track of the particles
interacting with each other. We can also work backward,
finding the mass from knowing the
One mole is the amount of a
number of moles. If we have 4
substance that has the same
moles of H 2SO 4, how many grams
number of particles as found in 12
is that?
grams of carbon C-12. How many
particles, you ask? First, look up H, S, and O in the
602,214,150,000,000,000,000,000 periodic table to find their atomic
particles to be precise. Or in masses:
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shorter notation: 6.022 x 10 H = 1, S = 32, O = 16. So the
particles. atomic mass of H 2SO 4 is:
This special number is called H 2SO 4 2H + S + 4O 2(1) + 32
Avogadro’s constant, and since + 4(16) = 98
“mole” is a lot easier to write than So one mole of H 2SO 4 weighs 98
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6.022 x 10 , chemists like to use
grams. Now use this conversion to
it to help keep track of the
find the mass for 4 moles:
particles in a chemical reaction. It’s
a handy way to convert between Grams of H 2SO 4 = 4 moles x (98
atoms and grams, or even grams/1mole) = 392 grams
molecules and grams. Here’s how: So there are 392 grams of H 2SO 4
Let’s figure out how many moles in 4 moles.
are in 500 grams of CO 2. First, we How to Measure Chemicals If
peek at the periodic table and find you’re going to do a chemistry
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