Mole Conversions Made Easy: How to Convert Between Grams and Moles
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Welcome to Mole Conversions Made Easy, brought
to you by Ketzbook. In this video, we are going to learn how to
do mole conversions for elements, how to calculate the molar mass of a compound, and how to do
mole conversions for compounds. But before we jump into all that, you might
be wondering…what is a mole? Well, there are lots of different moles in
the world, but in chemistry, a mole is simply a large number of things. It’s kind of like a dozen, only bigger. One dozen is 12 things. One mole is 6 times 10 to the 23rd things,
that is, 600 billion trillion things. Now, that’s a lot of things! But why is the mole such a big number? Because atoms are so small. Suppose you wanted to know how many hydrogen
atoms are in one cup of water. If you were able to count all the atoms, you
would find that there are about 15 trillion trillion hydrogen atoms in a cup of water. But if we count using moles instead, that
works out to be only 25 moles of hydrogen atoms. So, we use moles to count atoms, molecules,
and other chemicals. It turns out that there is an even better
reason why 1 mole equals 6 times 10 to the 23rd things. And that is that one gram equals 6 times 10
to the 23rd atomic mass units. Let’s see what this means for a particular
element. Break out your periodic table, and look for
lithium. It is the third element. On the bottom of the square, you should see
the number 6.94. This is the atomic weight of lithium. But it is also the molar mass of lithium. So, one lithium atom has an average mass of
6.94 amu, AND one mole of lithium atoms has a mass of 6.94 grams. That give us a convenient way to count atoms
by weighing them, and the molar mass is the conversion factor between grams and moles. Let’s try a problem. How many moles of lithium are in 25 g of lithium? This is a one step unit conversion problem,
and like any unit conversion problem, the first thing you should do is write down the
quantity that you know… in this case, 25 grams of lithium. Next, multiply this by a conversion factor
fraction. Remember that for mole conversions, the molar
mass is always our conversion factor. One mole of lithium equals 6.94 grams. Because we started with grams, we put the
6.94 grams on the bottom of the fraction. Grams on the top and bottom cancel each other
out. Next, write one mole on the top of the fraction. Because the one is on the top of the fraction,
this becomes a division problem. In your calculator type 25 divided by 6.94. The answer is 3.6 moles of lithium. You may have been wondering, what happened
to the “e” in mole? Well, it turns out that the abbreviation of
mole is M-O-L. Isn’t it just wonderful how much energy
we are all going to save by not writing the “e”? Okay, time for another sample problem. What is the mass of 11.5 moles of lithium? Before we solve this problem, we realize that
mass is measured in grams, so we need to convert from moles to grams. The first thing you should do is write down
the quantity you know, 11.5 moles of lithium. Next, multiply this by a conversion factor
fraction. The molar mass of lithium is still the conversion
factor. Because we are starting with moles, one mole
goes on the bottom and 6.94 grams goes on the top. Moles on the top and bottom cancel each other
out. Because the one is on the bottom of the fraction,
in your calculator type 11.5 times 6.94. The answer works out to be 79.8 grams of lithium. That is how to convert between moles and grams
for elements, but what about molecules and compounds? Let’s start by looking at molecules made
from carbon, nitrogen, and oxygen. The molar mass of each element is typically
written on the bottom. Now in order to convert between grams and
moles for a molecule, we will need to calculate the molar mass of the molecule by adding up
the molar masses of all the atoms in the molecule. Let’s try a few examples. Carbon monoxide has one carbon and one oxygen,
so we add 12.01 for carbon and 16 for oxygen to get a molar mass of 28.01 grams per mole. In general, the units of molar mass are grams
per mole. However, it is very useful to write the molar
mass as an equality. One mole of carbon monoxide has a mass of
28.01 grams. That helps us to remember that the molar mass
is a conversion factor. Let’s try another molecule. Nitrogen is a diatomic element composed of
N2 molecules. Because there are 2 nitrogen atoms per molecule,
we multiply 14.01 by 2, so the molar mass of N2 is 28.02 grams per mole. For carbon dioxide, there is one carbon and
two oxygen atoms. So, we add 12.01 for carbon and 16 times 2
for the two oxygens, which gives us a molar mass of 44.01 grams per mole. We can do the same thing for ionic compounds,
like magnesium nitrate. The molar mass of magnesium is 24.3. Because there are two nitrates in the formula, that means we have 2 nitrogen atoms and 6 oxygen atoms. So, we add 24.3 plus 14.01 times 2 plus 16
times 6, which works out to be a molar mass of 148.3 grams per mole. Remember that we can write the molar mass
as an equality, so for magnesium nitrate, 1 mole equals 148.3 grams. That is our conversion factor between grams
and moles. So let’s go ahead and use this molar mass
to do some mole conversion problems. Let’s convert 6.35 grams of magnesium nitrate
to moles. We will solve this problem in exactly the
same way that we converted grams of lithium to moles of lithium. First, write down the quantity that we know,
6.35 grams of magnesium nitrate. Next, multiply this by a conversion factor
fraction. The molar mass of magnesium nitrate is our
conversion factor. Because we started with grams, write 148.3
grams on the bottom. Because we are solving for moles, write one
mole on the top. Grams on the top and bottom cancel out. Because the one is on the top, in your calculator
type 6.35 divided by 148.3. This works out to be 0.0428 moles of magnesium
nitrate. What if we want to know the mass of 0.369
moles of magnesium nitrate? First, write down the quantity that we know,
0.369 moles of magnesium nitrate. Next, multiply this by a conversion factor
fraction, using the molar mass as the conversion factor. Because we are starting with moles, put 1
mole on the bottom; and because we are solving for mass, put 148.3 grams on the top. Moles on the top and bottom cancel each other
out. Because the one is on the bottom of the fraction,
multiply 0.369 times 148.3, which gives us 54.7 grams of magnesium nitrate. Thanks for watching. If this video helped you at all, please give
me a thumbs up. It means a lot to me. Feel free to also share any comments or questions
you have below, subscribe to my channel, or check me out at ketzbook.com.

100 thoughts on “Mole Conversions Made Easy: How to Convert Between Grams and Moles

  1. How about questions like these? I understand what's in the video but not this… is it a whole different concept?

    How many moles of sodium hydroxide (NaOH) will be produced from the complete reaction of 15.0 g of sodium
    2Na+2H2O->2NaOH+H2

  2. I have been struggling with this concept for like 3 weeks thanks for making more understandable you are a grade saver!!!!!!!

  3. The explanation in this video on this subject was very helpful. It helped my son understand a whole lot easier how to do the conversions. I think he did an awesome job breaking this down. Thank you.

  4. Thankuu so muchhh for dis video my doubt is clear now nd i able to solve the question thnkku so much ones again💐😊

  5. Thank you so much!! My chemistry teacher is new to teaching, and he over explained this and I got really confused, and so did most of my class. Everyone was asking each other, "Do you get this?" and people we always say no, including me. My friend told my teacher she had no idea how to do it he re-explained it but it didn't help at all cuz the way he explained it was super confusing, so I just decided to look it up on youtube, and this video popped up, so I watched it, and wow! Converting moles is so much easier now! I didn't realize it was so simple, and I was over here thinking I was gonna fail chemistry. Thanks for the help 😀

  6. Omg thank you 🙏this is so helpful. I watched so many other videos and I got so confused. Now I understand for once😂

  7. Th best video ever! I have a quiz tomorrow and you saved my grade,
    Thank you so much, your videos do help a lot. 😃

  8. Thanks for this video! I hope it saves my chemistry grade for tomorrow’s test! It sucks because we are doing seven different ways all on one test! It includes stuff about STP, empirical formulas, percent composition, molecular formulas, ugh, half the time I don’t even know where to write the numbers at but I think you explained it sooo well! Thanks for the help!

  9. My chemistry teacher is a long term sub, used to teach college, retired FBI agent and he is so bad and explaining and teaching this stuff. Thank you!

  10. I really liked how you mentioned to write the molar mass as an equality, it helped me connect where to put the numbers when converting!

  11. n=m/M makes every conversion problem so easy. Thank you. Now when I fill in the blanks, its just a simple algebra problem. Why do Chemists ignore the easy???You must be a mathematician.

  12. THANK YOU 🙏 You just explained in 7 minutes what my teacher couldn’t explain in a week and a half!! You just saved my chem grade!!

  13. i have struggled with this mole thing 4 longer than 6 months. then this guy explained it in 7 min and all the sudden it makes sense…. ooff…

    this guy should get an award for this >o<

  14. If you're going to round numbers, especially in a video designed to introduce/simplify a topic, you should tell people first. Otherwise, nice explanation.

  15. u explained this better than my teacher in a 7-minute video than she did throughout the whole semester, thank you so much!

  16. i was terrified for my chem test because my teacher didn’t really explain it well, now i finally get it and i’m about to send this to all my friends😂

  17. THANK YOU SO MUCH FOR MAKING THIS!!! I literally have a chemistry test tomorrow about this and I had no clue how to convert, but after watching this I completely understand now.

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