How To Do Molar Calculations

Hi, I am Donald Sinclair, one of the tutors of Greater London Tutors. Now I am going to teach you about a few of the topics of chemistry. This is how to do molar calculations.

A mole is a unit that tells how much something it is. It is defined as 6*10 power23 atoms or ions or molecules. 6*10 power 23 of course is 6 followed by 23 zeroes which is very a large number because atoms, ions or molecules are very small.

It is a proper use of large number. This is called Avogadro's number, after the scientist who first came up with it. This means if you have one mole of water for example, that means 6*10 power 23 water molecules.

Now, the real formula of moths of an atom or molecule tells you how much one mole of that will weigh in grams. so for example, if you have one mole of magnesium, that means you have 6*10 power 23 magnesium atoms weigh 24 grams. If you want to calculate the formula for molecules, it is very easily.

So for example, water one molecule contains 2 hydrogen atoms and 1 oxygen atom, which is 1+1+16, so the real formula of maths is 18 .This means one mole of water will weigh 18 grams. Let us look at the example, what are the ideas that most arouses to Maths is involved in chemical reactions.

For example, here we have the reaction of magnesium oxide. Now it is already been balanced and the numbers tell you how much or how many moles of that substance were reacting with the other. So for example, we see that 2 moles of magnesium reacts with one mole of oxygen molecules to form two moles of magnesium oxide molecules.

Now we find maths is involved here. 2 moles magnesium have a maths of 48 grams since one mole of magnesium has 24 grams. One mole of oxygen molecules will have a maths of 16 times 2 equals 32 grams.

One mole of magnesium oxide will be 24+16 equals 40 and because of two, we have a total maths of 80 grams. Always maths on the left hand side should equal the maths on right hand side. So here 48+32 equals 80 which are on right hand side.

So let us say to workout, if we have 3 grams of magnesium reacting with x grams of oxygen and 4 grams of magnesium oxide will have at the end. We workout in this way ,we know that one mole of magnesium have a maths of 24 grams, so if you have 3 grams it is 3/24 which is 0.125 moles is reacting.

You see 2 moles of magnesium will give 2 moles of magnesium oxide .In other words, 2:2 ratio which is 1:1 ratio. So 0.

125 moles of magnesium reacts and give 0.125 moles of magnesium oxide. Now 0.

125 which is number of moles multiplied by one mole which is 40 get grams. So we get 5 grams of magnesium oxide and 3 grams of magnesium reacting with oxygen. .