Calculation of Molecular Mass
Molecular mass is predicted by multiplying the number of atoms with the atomic mass of an element in the molecule and then adding the masses of all the elements in the molecule.
- Make sure to analyze the chemical formula to determine the number of atoms of each element in the compound.
- Multiply the number of atoms present in the compound by the atomic weight of each element.
- Add up all the mass and assign its unit as grams/mole.
Example 1: Determine the Molar mass of CO2.
Answer:
First Calculate the number of each atom, and assign their atomic weight individually
The number of carbon atoms × its atomic mass: 1 × 12 = 12
The number of oxygen atoms × its atomic mass: 2 × 12 = 24
Then add the values i.e., 12 + 24= 36
Therefore the molar mass of CO2 is 36 g/mol.
Example 2: Determine the formula unit mass of CaCl2.
Answer:
The formula unit mass of CaCl2 = Atomic mass of Ca + 2 × (Atomic mass of Cl)
formula unit mass of CaCl2 = 40 + 2 × 35.5
formula unit mass of CaCl2 = 40 + 71
formula unit mass of CaCl2 = 111 a.m.u.
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Molecular Mass
Molecular Mass is the mass of all the atoms present in a molecule. In ancient India and Greece, philosophers have first given the idea of atoms and deeply studied them. Around 500 BC.
Everything around is made up of very small units these units are atoms in the language of science, very small in the sense is in the range of 0.1 – 0.5 nanometers. These atoms join to form molecular which then join to form matter. For example, two atoms of hydrogen and one atom of oxygen joins to form one molecule of H2O which is water. Hence, the molecular mass in this case of H2O will be given as sum of mass of two atoms of hydrogen and one atom of oxygen.
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