Moles in formulae and equations

We know that one mole of any particles, atoms, molecules or oranges would contain 6 x 1023 particles. The mole has been chosen as a unit because, one mole of atoms has a mass equal to their atomic mass in grams, e.g. the atomic mass of carbon is 12, so one mole of carbon = 12 g. 

One mole of molecules will have a mass equivalent to their molecular mass in grams. One mole of sodium chloride, NaCl (Na = 23, Cl = 35.5) = 58.5 g, and one mole of alcohol, C2H5OH (C = 12, O = 16, H = 1) = 46 g. These 46 g of alcohol will contain the same number of particles as 58.5 g of sodium chloride or 12 g of carbon. 

One mole of any atom or molecule will have a mass of its atomic or molecular mass in grams. This means that 12 g carbon will contain the same number of atoms as there are molecules in 58.5 g sodium chloride. 

This is how we know how to balance chemical equations and work out the masses reacting together, because we know that equal molar masses contain the same numbers of particles. In a chemical equation like C + 02 — C02, we always know that there will be one mole of carbon atoms reacting with one mole of oxygen molecules (02) to give one mole of carbon dioxide. Providing the chemical equation balances, any fraction of moles will also be true. One-tenth of a mole of carbon will require one-tenth of a mole of oxygen gas molecules (02), to make one-tenth of a mole of carbon dioxide gas (C02). 

Therefore 10 moles of alcohol have a mass of 460 g and likewise 10-2 moles of alcohol have a mass of 46 x 10 2 = 0.46 g = 0.46 g. 

---