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[Chemical Knowledge]：How to calculate the molecular weight

Read： 1898 Time：18months ago Source：Transform the World with Simplicity

Molecular weight is a measure of the relative molecular mass of a molecule, which is the sum of the relative atomic masses of all atoms in the molecule. The calculation of molecular weight is very simple, only need to know the chemical formula of the molecule and use its relative atomic mass. In this article, we will introduce the calculation method of molecular weight in detail and some practical examples. The calculation method of the molecular weight of the

the calculation of the molecular weight of the
involves the chemical formula of the molecule, and the molecular formula is indicated by the symbol of the element and the number of the element. For example, the chemical formula of a water molecule is H₂ O, where there are two hydrogen atoms and one oxygen atom. Now, we can use the relative atomic mass of each atom to calculate the molecular weight of the water molecule.

calculate the molecular weight of water molecules

In order to calculate the molecular weight of water, we need to know the relative atomic mass of each atom and add them together. According to the periodic table, the relative atomic mass of a hydrogen atom is 1.01 and that of an oxygen atom is 16.00. Therefore, the molecular weight of the water molecule is calculated using the following formula:

molecular weight = 2 x 1.01 16.00=18.02

We conclude that the molecular weight of the water molecule is 18.02.

In the example above, we used the chemical formula of the water molecule, knowing the number of hydrogen and oxygen atoms and their relative atomic masses, and added together to calculate the molecular weight of the water molecule. We can use the same method to calculate the molecular weight of other molecules.

calculate the molecular weight of other molecules

Now, let's calculate the molecular weight of another simple molecule-methane (CH4). The chemical formula of methane consists of one carbon atom and four hydrogen atoms. According to the periodic table, carbon has a relative atomic mass of 12.01, while hydrogen has a relative molecular mass of 1.01. Therefore, the molecular weight of methane is calculated using the following formula:

molecular weight = 1 × 12.01 4 × 1.01=16.05

We conclude that the molecular weight of methane is 16.05.

In practice, molecular weight is very useful. It provides us with information about the physical and chemical properties of molecules and helps us design reaction schemes. For example, understanding the molecular weight of ethanol (CH3CH2OH) can be used to calculate how much ethanol is needed to make a given amount of an ester compound.

In this article, we have understood the basic principles of molecular weight calculation. In practice, of course, the calculation of the molecular weight may be more complex, as multiple molecules may make up complex systems. However, when you master the basic principles of molecular weight, these calculations will become easier.