Molecular Weight Calculator

Common Organic Compounds

Elements of the periodic table

Chemical formula:

# Atom Molar Mass (MM) Subtotal Mass Subtotal Mass
(g/mol) (%) (g/mol)

Total Molecular Weight:

About Molecular Weight Calculator

What is molecular weight and its unit?

A molecule's weight is its molecular mass. Since molecular weights are measured in units of mass, which are not weights at all, the term "weight" is actually a little deceptive. Because of this, molecular mass or formula mass are more appropriate names for molecular weight. The unit of measurement used to characterise a molecule's mass is its molecular weight. Combining the atomic weights of each atom in a molecule yields the molecular weight. Each element has a unique atomic weight that corresponds to the average of its atomic mass. Because each element has distinct isotopes with somewhat differing atomic weights, an average is determined for each. The mass of a material or molecule is frequently determined using a mass spectrometry equipment.

How to calculate molecular weight?

The standard chemical unit for expressing how much of a compound is present is the mole. The unit used to measure a substance's quantity is called a mole. The number of entities in one mole of "something" is 6.022 x 1023. One mole of a chemical substance, for instance, has 6.022 x 1023 molecules.

Since water has the chemical formula H2O, this molecule consists of 3 atoms: 2 hydrogen (H) atoms and 1 oxygen (O) atom. We may determine the atomic weights of the elements using their periodic tables, and we discover that hydrogen has an atomic weight of 1, while that of oxygen is 16. We sum the contributions from each atom to determine the molecular weight of one water molecule, which is 2(1) + 1(16) = 18 grams/mole.

Ethylene monomers have the chemical formula (CH2-CH2). Two carbon (C) atoms and four hydrogen (H) atoms make up its total of 6 atoms. One mer of ethylene weighs 2(12) + 4(1) = 28 because the atomic weight of hydrogen is 1, and the atomic weight of carbon is 12. To create a polyethylene chain, we react a lot of ethylene mers collectively. It would weigh 28,000 grams/mole and have 6,000 atoms if 1,000 mers were joined together.

What is atomic weight?

The average mass of an element in relation to all of its isotopes and their relative abundances is known as its atomic weight. Atomic mass, commonly referred to as daltons, is used to measure atomic weight. Multiple isotopes of the same element are possible. It is vital to take the masses of isotopes into account while calculating atomic weight. Different isotope ratios could exist. Isotope relative abundance and isotope mass must be taken into account when computing atomic weight. The ratio of the average mass of the atoms in a chemical element to a predetermined standard is known as atomic weight, also known as relative atomic mass. Since 1961, the standard measure of atomic mass has been one-twelfth of the atomic mass of the carbon-12 isotope.

What is the difference between molar mass and molecular weight?

The term "molar mass" refers to the mass of a mole of a certain substance, which is the mass of the compound in question divided by the substance's mass. It is a feature of how things are physically. The atomic mass of an element is the element's molar mass. The atomic masses of all the elements that make up a molecule are added to determine the substance's molar mass.

The same or different atoms can be combined in varying ratios to form molecules, which are physical entities. To create compounds, these molecules joined forces. In addition, the molar mass and molecular weight of substances are two physical characteristics. It is crucial to comprehend the chemical and physical characteristics of molecules in order to carry out chemical processes and predict the results because nearly all chemical reactions involve changes occurring in molecules or compounds. Additionally, the primary distinction between the two is that molar mass provides the mass of a mole of a certain substance. In contrast, molecular weight refers to a substance's molecule's mass. While molar mass and molecular weight have different definitions and measurement systems, their values are equivalent.

What is the molecular weight of water?

Knowing a compound's molecular formula and the atomic weight of each type of atom that makes up a molecule allows us to compute the molecular weight of any substance. The molecular weight of the molecule can then be determined by adding the atomic weights of all the atoms that are part of it. A compound is created when a collection of atoms come together in a particular arrangement, and the smallest essential component of a compound is called a molecule. A compound's molecular formula is a chemical formula that specifies how many atoms of each element are contained in the compound's molecule.

The atomic masses of O and H are 16 g/mol and 1 g/mol respectively.
The molecular formula of water is H2O and its molecular weight 2(1)+16=18 g/mol.

What is molecular weight of air?

Typically, the air contains a mixture of many gases, including carbon dioxide, oxygen, nitrogen, and argon. The two gases that predominate in dry air, which is a mixture of many gases, are 21% oxygen and 78% nitrogen, along with 0.934% argon and roughly 0.03% carbon dioxide.

The two gases that predominate in dry air, which is a mixture of numerous gases, are 21 vol% oxygen and 78 vol% nitrogen. The molar masses of nitrogen and oxygen are respectively 15.9994 and 14.0067 g/mol. O2 and N2 are both diatomic in air, hence their molar masses are approximately 32 g/mol for oxygen and 28 g/mol for nitrogen, respectively. The average molar mass is determined by adding the mole fractions of all the gases together and multiplying the result by the molar mass of that specific gas. As a result, the following elements have the following atomic weights.

Nitrogen – 28.0134 g/mol

Oxygen – 31.9988 g/mol

Argon – 39.948 g/mol

Carbon Dioxide – 44.01 g/mol

each gas's weight using its proportion

Nitrogen – 21.8739 g/mol

Oxygen – 6.7025 g/mol

Argon – 0.373 g/mol

Carbon Dioxide – 0.013203 g/mol

The values we obtain from the gas's weight mentioned above must now be added. Obtaining 28.96 g/mol. As a result, the molecular weight of air is 28.96 g/mol.