Definition of
Molecular mass
The first thing that should be done before fully entering into the definition of the scientific term that concerns us now is to proceed to establish the etymological origin of the words that make it up in order to better understand its meaning.
Specifically, we can state that it is made up of two words that come from Latin. The first of them, massit derivates from massa which in turn comes from the Greek madza which was the word used to refer to a delicious cake that was made mainly using flour as an ingredient.
Molecularfor its part, is a diminutive term that comes from the union of the Latin word moles which can be translated as “mass” and the suffix –culum whose meaning is “small”. Hence, when speaking of a molecule, reference is made to what a small mass is.
- The concept of molecular mass
- sum of atomic weights
- molecular mass formula
- Related Topics Tree
The concept of molecular mass
Mass is a magnitude of a physical nature that reflects how much subject is contained in a body. In it International systemits unit is called kilogram (kg.).
Molecularfor its part, refers to what is linked to the molecules (the smallest particle that has the totality of the chemical and physical properties of a substance).
It can help you: Atomic mass
sum of atomic weights
according to dictionary of the Royal Spanish Academy (RAE), the concept of molecular mass is synonymous with molecular weightwhich is the sum of the atomic weights that make up the molecular formula of a certain compound. At present, in any case, the notion of molecular mass is used and not that of molecular weight.
Molecular mass, in other words, is the sum of atomic masses in a molecule. To calculate it, it is necessary to know the atomic masses of each of the elements that are part of the compound.
When making the aforementioned sum, it is important that we know that if the decimal figures are greater than 0.5, then what the mass number will do is approximate the whole unit that follows it. We can verify or exemplify this with the corresponding number of oxygen that we see, which is 15,999, which means that in the end it is established that said number is 16.
See also: Chemical formula
molecular mass formula
Starting with one of the sides of the formula, we must multiply the subscript of each element by its atomic mass. Once all the multiplications have been completed, the results must be added and in this way the molecular mass is obtained, expressed in atomic mass units (uma).
The molecular mass coincides in number with the molar massalthough these are different things. The molecular mass allows us to know the mass of a molecule, while the molar mass reflects the mass of one mole of compound.
In the case of molar mass we have to determine that there are various classes of it. Thus, we find the molar mass of the compounds, that of the elements or that of the average of mixtures.
Take the example of the molecular mass of water. The chemical formula is H20Two hydrogen atoms and one oxygen. The atomic mass of hydrogen is 1 amu, while the atomic mass of oxygen is 16 amu. The molecular mass of water, therefore, is (2 x 1 amu) + 16 amu = 18 amu.
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