The molecule is the smallest unit of a substance that still retains the characteristics of this substance. It has very small sizes, it cannot be viewed with a naked eye or weighed. How to calculate the mass of the molecule?
Mole and atomic weight of the molecule
To calculate the mass of the molecule, the unit, called mole, and the measurement called atomic weights are used. Mole is a magnitude equal number Avogadro, which is approximately 6.022 x 10 ^ 23. Atomic weight is the weight of one atom of a substance in units of atomic mass. The weight of one praying of the element is equal to the atomic weight of the element. Knowing it, it is possible to remove the mass of each molecule from its chemical formula and atomic weights of its elements, as described in the periodic table.
Install the chemical formula of the molecule
To calculate the mass of water molecules, you must first find out its formula - H20:
- Find the atomic weight of each atom in the molecule. You can find this information in the Periodic Table; This is usually a decimal number indicated above or below the symbol of the chemical element.
- For example, the atomic weight of hydrogen is 1.0079, and the atomic mass of oxygen - 15.9999. One mole of each element weighs the same amount in grams.
- Further, based on the formula already known to us, we calculate the sum of all molecule atoms.
- In particular, the water molecule contains two hydrogen atoms and one oxygen atom. In this case, the molar mass of the water is equal to 1,0079 + 1,0079 + 15,9999, or 18,0148 g. Mole (g / mol).
- Divide the sum of molecules to mole or the number of Avogadro (6.022 x 10 ^ 23).
- For example, 18.0148 / 6.022 x 10 ^ 23 \u003d 2.991 x 10 ^ 23. Thus, one water molecule weighs 2.991 x 10 ^ 23.
As can be seen from the above example, using a periodic table of Mendeleev, you can get all the necessary indicators to calculate the mass of molecules of various substances.
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