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The Mole

The mole is defined as the number of carbon atoms in exactly 12g of pure carbon-12. Mass spectrometry which count atoms very precisely have determined this number 6.022×10^23. This number is called Avogadro's number. One mole of something consists of 6.022×10^23 units of that substance. Just as a dozen eggs is 12 eggs, a mole of eggs is 6.022×10^23 eggs. Molar mass is the mass in grams of 1 mole of the substance. There are two common ways of describing the composition of a compound: In terms of the number of its constituent atoms and in terms of the percentages by mass of its elements. We can obtain the mass percents of the elements from the formula of the compound by comparing the mass of each element present in 1 mole of the compound to the total mass of 1 mole of the compound.