Mole Concept

Let's say you go shopping and your shopping list is 3 kg of potatoes 2 liters of juice and 1 dozen oranges Now what are these things on your list? kg liter dozen, that's right, are units that we use in our daily lives. to measure the amount of things but now suppose I add 1

mole

of salt to your shopping list then do you know how much you need to buy? Do you know how much a

mole

is? Now don't go to the store and ask for a mole. of salt because it's not an everyday unit, you're going to get confused, it's the chemistry guy's unit and that's the only goal of this video is to really understand how much a mole is and then we'll finish with our three main exam-oriented questions. on this topic, do you have an idea how much is 1 kg of salt?

Next time you go shopping, you can check the salt packets. It usually says 1kg. Do you know how much a gram of salt is? Let me show you that this pool contains about one. gram of salt, but the question is how much is a mole of salt. One mole is defined as the molecular mass in grams. Let's analyze this definition. Molecular mass is the mass of a molecule and the substance here is salt, so to calculate the molecular mass we need to I need the molecular formula, so what is the molecular formula of salt? That's right, it's NaCl.

If you want to find the molecular mass, I need to use the atomic mass of sodium and chlorine, which are 23 and 35.5 respectively, but I'm going to approximate chlorine as 35 so the total mass of salt is 58 now this is the relative molecular mass we need to take the molecular mass in grams so one mole of salt is 58 grams let's go ahead and measure 1 mole of salt Here I am measuring one mole of salt and as you can see, it is exactly 58 grams. Note that the mass of the container is subtracted. Let's take the example of a liquid.

So how much is a mole of water? Water has the molecular formula h2o. The atomic mass of hydrogen is 1 and oxygen is 16. so the total molecular mass is 2 in 1 plus 16, that's 18, so one mole of water will weigh 18 grams and here I have it ready for you, so I have one mole of water here and, as you can see, it's exactly 18 grams. take the example of a gas like oxygen, let's say this flask contains 1 mole of oxygen, then what will be the mass of oxygen in this flask again? We need to take the molecular mass in grams.

Oxygen has the formula o to the atomic mass is 16. so, the molecular mass of oxygen will be 32, so one mole of oxygen in this jar will weigh 32 grams, so here on the table we have 1 mole of salt, which is 58 grams, 1 mole of water, which is 18 grams, and one mole of gaseous oxygen. which is 32 grams, as you can see, one mole of different substances has different masses because it depends on the molecular mass. The mole is often written as Moll or mol l, in short, so a mole is the molecular mass in grams and is also known as molar mass.

Let's put this definition of mole based on molecular mass on our

concept

board. The mole can not only be expressed in terms of mass but also in terms of the number of particles, which is the number of molecules present in the substance, obviously, the number of molecules. It's going to be really very very large because each molecule is very, very, very small, so we can't expect to count the number of molecules that we need to estimate it, so if you think about it, how are we going to estimate the number of molecules present ? In these one mole samples we can use the formula the number of molecules is the mass of the substance divided by the mass of one molecule.

Let's start with salt, so the number of molecules is the mass of one mole of salt divided by the mass of one salt. molecule The mass of a mole of salt is the molar mass in grams, so it is 58 grams and the mass of a molecule of salt is 58. This is the relative molecular mass, which means it is 58 times heavier than a hydrogen atom and a hydrogen atom has the mass one point 6 7 times 10 to the power minus 24 grams if we connect those numbers and divide we will get six point zero 2 2 times 10 to the power 23 molecules of salt similarly, we can calculate the number of molecules present in one mole of water, the number of water molecules will be the molecular mass of water in grams divided by the mass of one molecule of water similarly, the number of oxygen molecules will be the molecular mass of oxygen in grams divided by the mass of one molecule of oxygen, so if we plug in the numbers we will get the same number, in fact, no matter what substance you take, you will get the same number of molecules in one mole of any substance which is 6.022 times 10 raised to 23 molecules.

This special issue is known as Avogadro. constant or number of avocados in some textbooks you may find it as 6.02 3 times 10 to the 23rd power. Let's spin this definition of a mole based on the number of molecules on our

concept

board. Now let's take a look at what the volume occupied by one mole of a substance is, but remember that this works only for gases, not solids or liquids. One mole of any gas occupies twenty 2.4 liters in STP. That's right, it works for any gas. Do you know what the meaning of STP is? It means standard temperature and pressure. temperature means the temperature is zero degrees centigrade and the standard pressure is one atmospheric pressure or the normal pressure we feel on the surface of the earth so suppose I set my room in STP conditions now the pressure is one atmosphere and it is zero degrees centigrade, so it's It's really cold right now and just wait.

I need to go and grab my jacket. Ah, that's much better now, so let's continue. Let's take the example of a gas like oxygen. So how much volume will one mole of oxygen gas occupy under STP conditions? That's right 20 2.4 liters so to visualize this volume I'm sure you've seen these 1 liter water bottles so you can imagine 22 of these bottles which is the amount of volume that the oxygen will occupy in STP where we are taking 1 mole of gas oxygen, in fact, 1 mole of any gas, be it oxygen, hydrogen, nitrogen, carbon dioxide, they all occupy 22.4 liters in STP, this is called molar volume.

Let's put this definition of 1 mole based on the volume of a gas in our concept board, let's say I want 1. mole of oxygen since it is a gas, I have the three options to measure it, that is, the mass, the number of molecules and the volume occupied by the gas, so if I use mass then I need 32 grams of oxygen gas if I am using counting. of molecules then you would need 6.022 times 10 to the power of 23 oxygen molecules and if I use volume then it will be 20 2.4 liters of oxygen gas at STP of course counting the molecules is impossible so we usually use mass or volume when They are measuring a gas to help remember this important relationship.

You can learn this sentence. 1 mole of any substance is equal to the GMM, which is the gram of molecular mass, and that is equal to 6 points from 0 to 2 between 10 to the power of 23 molecules and that is. equal to 22 point 4 liters in STP if it is a gas now that we have finished the mole concept, are you ready to move on to our three main questions on this topic? Here are the top 3 questions. I encourage you to pause here and try to resolve. these questions, I will soon post a video about the solution. You can find a link to the solutions video in the description below or search for it on my channel page, so I hope the concept of mole is really clear to you now that we have learned in this video that it is a very useful unit in chemistry , so now you can be a chemistry expert and write your shopping list in moles and confuse everyone and don't forget to like, comment, share this video and subscribe to my channel.