Summary of main points about defining and using the mole concept For the purposes of calculations chemical amounts are primarily measured in moles but sometimes just masses are ok. The symbol for the unit mole is mol and the mass of one mole of a substance in grams is numerically equal to its relative formula mass can be atomic mass or molecular mass - see below.
This might be an atomic mass of an element e. One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance. So all the three described above have the same number of defined particles. The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant.
The value of the Avogadro constant is 6. So the four examples described above equate to 6. The latter consists of 2 x 6. You must be versatile in your mol thinking! You should understand and how to use measurement of the amounts in moles and apply this knowledge to calculations involving atoms, molecules, ions, electrons, formulae and equations. This is a lot to take in, so I've described in details lots of examples explained below on how to use the 'mol' The 2nd part of the heading is 'easy', the first part is a bit more 'abstract' to get your head round!
The mole concept is an invaluable way of solving many quantitative problems in chemistry! Its a very important way of doing chemical calculations! The theoretical basis is explained in section b. The mole is most simply expressed as the relative 'formula mass in g' or the 'molecular mass in g' of the defined chemical 'species', and that is how it is used in most chemical calculations. The mass of one mole of a substance is sometimes referred to as the molar mass.
If your are dealing with individual atoms, one mole of equals the relative atomic mass in grams. This can be expressed as a simple formula This specificity cannot be overemphasised and you should understand that the measurement of amounts in moles can apply to atoms, molecules, ions, electrons, formulae and equations!!! The term relative molecular mass sum of the atomic masses of the atoms in a single molecule of the substance is usually applied to definite molecular species. Using the following atomic masses: The term relative formula mass sum of the atomic masses of the atoms in a specified formula can be used for ANY specified formula of ANY chemical substance, though it is most often applied to ionic substances.
Set 1 of mole calculations - using the simple mole formula see triangle relating mass, moles and relative formula mass Simple mole calculations Example 7. Or you could say 2 moles of ammonia is formed from 1 mole of nitrogen molecules N2 combining with 3 moles of hydrogen molecules H2. The latter is a better way to look at ammonia formation because nitrogen and hydrogen exist as diatomic molecules and NOT individual atoms. So, you can calculate using any mole ratio on the basis of the 1: Mole calculation Example 7.
You read the equation in relative numbers of moles and convert the moles into mass. Using the concept of mole ratio and the exemplar reactions above From the equation, 1 mole of copper oxide makes 1 mole of copper chloride, therefore you need 0. Set 2 of mole calculations - relating a formula and equations to the mole concept Mole calculation Example 7.
So there will be 0. So there will be 2. Calculate its molecular mass. The final mass of the iron oxide was There was only one product of the reaction.
O2 ratio to the simplest whole number ratio Fe: Convert the masses to moles and deduce the balanced equation from the mole ratios calculated.
Convert the reactant and product masses to moles and deduced the balanced equation.