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In this video we are going to preform unit conversions for molar in cases we wanted to
go from say gram moles to kilogram moles or kilogram moles to pound moles. Then you might
be thinking why do we have to have all these types of units for moles, and it comes about
that talking about large scale industrial processing. We don't necessarily talk about
how many gram mole (gmol) of a product we are producing. Were as if we are in a lab
working on a bench top in a small flask maybe gmol is an appropriate unit for the amount
we are working with. So this can be one of the more confusing conversion that we do,
but hopefully after this video, you will see that it is pretty straight forward. With any
conversion we use a conversion factor, and in this case the one that instantly pops into
mind is molecular weight, which reports molar mass of an element, or species, and what were
we have seen this in previews chemistry lessons is typically as grams per mole of whatever,
and what does this mean again? This means that we if we had lets say oxygen then we
now that the molecular weight is 32, but that means weight 32 grams for one mole of oxygen,
but what is one mole of oxygen. That is 6.023 times 10^23 atoms. So if we had that many
atoms of oxygen it would have a mass of 32 grams. So here it were it gets fun. We have
one gram per mole or 1 g/gmol this is equivalent to 1 lb/lb*mol, and you are thinking wait
what wait this does not imply that a gmol equals 1 lbmol. That is NOT true. So we know
a gmol is a certain amount of atoms. So a lbmol is not that many atoms. What this means
it that if we had a certain amount of atoms that comprise what is called a lbmol it is
going to a mass of a lbmol. Alright lets just get straight into an example, to see how this
works. Lets say we have 500 moles of oxygen and this is entering some imaginary tank and
leaving at the same rate. We want to know how many kgmol/hr, how many lbmpol/hr, how
many gmol/hr are leaving this tank. So for the sake of conversions. A mole can be written
as a mol or as a gmol all the same thing. So 500 moles an hour of O2 is equal to 500
gmol O2 per hour. Now if we want to go to say kmol we know that 1 kmol is 1000 moles.
So 500 moles of oxygen per hour times our conversion factor one over 1000 moles gives
us 0.5 kmol of oxygen per hour. So you have crossed of those two. Pretty straight forward.
Now you will rarely come across a kgmol, but if you are working with a large quantity in
an industrial experience you may see the kgmol. So how do we convert kgmol. Lets do it the
long way so we can see. We have 500 moles of oxygen per hour. Now if we multiply this
by our molecular weight of oxygen, which is our conversion factor. 32 grams of oxygen
per mole of oxygen we get 16000 grams of oxygen per hour, so now we have a mass flow rate
if that is what we wanted, but its not. So we need to go from this mass to our kgmol.
So we can convert grams to kilo grams. and we get 16kg of oxygen per hour, and we can
use our same conversion factor. We can take 16kg of oxygen per our divided by our conversion
factor molecular weight, which in this case is 32 kg of oxygen per kgmol, we get 0.5 kgmol
per hour. So you should notice something. These have the same value, but a kilogram
mole refers to 6.023x10^23 groups of 1000 atoms. If it were a mole it would be ten to
the 23 atoms. Which is up here. Here we saying we have 6.023 x10^23 atoms and we are using
a prefix to ask in terms of 1000. So basically, they are the same thing. So the last conversion
we are going to do is to convert to lbmol. So we want to know if 500 moles of oxygen
how many lbmol of oxygen we have flowing per hour. So lets use the same logic were we take
500 moles of oxygen per hour. Multiply it by our conversion factor of 32 grams of oxygen
per mole of oxygen, and we get 16000 grams of oxygen per hour. Now we take that 16000
grams and convert it to lbs, using the conversion factor of 454 grams per one lb mass. This
gives us 35.24 lb of oxygen per hour. Now we can then take 35.24 divided it by our conversion
factor, our molecular mass 32 lb/lbmol and we should get 1.1 lbmol per hour. Now the
short cut way to do this is by seeing that we are using our conversion factor twice.
So we could just jump those out of them. Show that the conversion really is just lb to grams
if we take 500 moles of oxygen per hour multiply it by 1 lb over 454 grams and just to make
sure the units look okay. You can see that we get the exact same thing. So to convert
from moles to lbmol we use our conversion of lb to grams.