Avogadro constant - Wikipedia
Mole and Avogadro's number (Khan, 9½ m) ** The mole How much heavier is the oxygen atom in relation to carbon? Solution: Atomic. The number of moles in a system can be determined using the can also be determined by using the relationship between grams, moles, and. Moles equation is moles= mass/RFM Avogadro's constant is 6.x 1 mole means 6x atoms/molecules. e.g. 2 mole of Cu weighs g. What is the.
Mole Video transcript Let's talk about a concept that probably confuses chemistry students the most on some level. But on some level it's also one of the simplest concepts.
And that's the idea of a mole, which in chemistry is different than the thing digging up your backyard, or the thing you want to get removed from your left eye.
A mole in chemistry is just a number. It's just a number, and the number is 6. So it's a very huge number.
And this is also called Avogadro's number. Maybe I will do a video on Avogadro. But that's all you need to know. A mole is just a number. There are kind of more Byzantine definitions of a mole. This actually is not-- actually, let me copy and paste it from Wikipedia. This is Wikipedia's definition of a mole. And you hopefully at the end of this video you'll see that they're equivalent. But if you're just getting exposed to the concept, this to me, it's just not an easy concept.
The mole and Avogadro's number
Basically, a "a mole is defined as the amount of substance of a system that contains as many elemental entities as there are atoms in 12 grams of carbon So if you just take the last part, atoms in 12 grams of carbon So that means that there are 1 mole of carbon let me write it like that-- carbon There are 1 mole of carbon 12 atoms in 12 grams of carbon. And so that's why a mole is useful. So I could have just instead of writing 1 mole, I could have replaced this as there's 6.
How do you figure that out? Or I guess, what else does this mean? I mean, we just added in carbon, they said it's the amount of substance of any molecule, if you convert between atomic mass units and grams.
This I find very confusing. How can we apply this in other places? So the first thing to realize is a mole is just a way of translating between grams and atomic mass units.
Avogadro's law - Wikipedia
One carbon 12 atom is what? What's its mass number? That's why it's called carbon 12 instead of carbon So its mass is 12 atomic mass units. So if you have something that has a mass of 12 atomic mass units and you have a mole of them, or you have 6.
So another way to think about it is 1 gram is equal to 1 mole of atomic mass units. I'll write amu's like that.
Or you can write 1 gram is equal to 6. And the reason why this is useful-- and it's kind of addressed in this Wikipedia definition there-- is it helps us translate between the atomic world-- where we deal with atomic mass units and we deal with, oh, we've got an extra neutron now, let's add one to our atomic mass number-- and translating between that atomic world and our everyday world where we deal in grams.
And just so you know, a gram is still a pretty small amount of mass. A kilogram is about 2 pounds. So this is not much. So there's a ton of atoms in a very small amount of-- in 1 gram of carbon, or at least in 12 grams of carbon, you have a ton of atoms.
And just to hit the point home, I probably should have talked about this in the atom. This is a huge number. To maybe visualize it, if you think of-- I was told that in the diameter of a hair, if this is a hair and this is diameter of the hair, if you go this way there 1 million carbon atoms.
Or if you were to take an apple and you were to try to figure out what fraction, if you were to make one of the atoms of an apple-- and obviously, an apple has a bunch of different types of atoms in it-- but if you were to take one of the atoms and make it the size of the apple, then the apple would be the size of the earth.
Molar volume of a pure substance This is the volume occupied by one mole of a pure substance. Molar volume depends on the density of a substance and, like density, varies with temperature owing to thermal expansion, and also with the pressure. This is definitely not the case with gases, whose molar volumes must be calculated for a specific temperature and pressure.
Calculate the molar volume of methanol.
The molar volume will be the volume occupied by one molar mass 32 g of the liquid. The idea is to mentally divide a piece of the metal into as many little cubic boxes as there are atoms, and then calculate the length of each box.
Assuming that an atom sits in the center of each box and that each atom is in direct contact with its six neighbors two along each dimensionthis gives the diameter of the atom.
The manner in which atoms pack together in actual metallic crystals is usually more complicated than this and it varies from metal to metal, so this calculation only provides an approximate value. Radius of a strontium atom The density of metallic strontium is 2.
The mole and Avogadro's number (video) | Khan Academy
Use this value to estimate the radius of the atom of Sr, whose atomic weight is The molar volume of Sr is The atomic radius will be half this value, or 1. You should also be able estimate the magnitude of this value for checking. The easiest way is to express the number so that the exponent is a multiple of 3.
So how good is our atomic radius? Standard tables give the atomic radius of strontium is in the range pm, depending on how it is defined.