what is analytical molarity ? please explain with example.

what is analytical molarity ? please explain with example.


1 Answers

34 Points
13 years ago

molarity is defined as "moles per liter". A mole is just a big number. Unlike "PI", nobody actually uses the number itself. Chemists rely on the fact this many atoms of any element has a characteristic weight. This is known as the atomic weight, and is found in the periodic table. What is true of atoms is also true of the molecules they make. The molecular weight of FeCl3 is the atomic weight of Iron (56 grams per mole) and three times the atomic weight of Chlorine (35 grams per mole). Thus a mole of FeCl3 weighs 161 grams per mole. Chemists then express amounts in terms of moles. 1.340 grams of FeCl3 represents 0.008 moles. If this amount of FeCl3 was added to 1 liter, the molarity would be 0.008 moles per liter. The concentration of the Chloride ions depends on how FeCl3 forms ions when it dissolves in water:

FeCl3 -> Fe(+3) + 3Cl(-)

The thing to note is that both the charge and the number of atoms is equal on either side of the "->" sign. Note also there are three chloride ions formed. Therefore, the molarity of the chloride ions is three times the molarity of FeCl3.

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