Key Difference – Formula Mass vs Molecular Mass

Formula mass and molecular mass are two terms supplied to uncover the mass of a molecule. The formula mass provides the mass of a molecule as soon as the empirical formula of that molecule is taken into consideration. The molecular mass provides the mass of a molecule once the molecular formula of that molecule is thought about. In both methods, the mass is calculated by adding the masses of each atom present in that formula. The primary difference between formula mass and also the molecular mass is that formula mass is calculated by including the masses of atoms existing in the simplest formula that have the right to be provided for a molecule whereas molecular mass is calculated utilizing the actual numbers of atoms existing in a molecule.

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Key Areas Covered

1. What is Formula Mass – Definition, Calculations through Instances 2. What is Molecular Mass – Definition, Calculations through Instances 3. What is the Difference Between Formula Mass and also Molecular Mass – Comparichild of Key Differences

Key Terms: Amu, Empirical Formula, Formula Mass, Mole, Molar Mass, Molecular Mass

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What is Formula Mass

Formula mass is the mass of a molecule calculated making use of the empirical formula of that molecule. The empirical formula is the formula that mirrors all types of atoms (elements) current in a molecule and their ratios. This indicates it represents the simplest formula that have the right to be given for a molecule. Sometimes, the empirical formula and also the molecular formula are the same for small molecules.

Calculation of Formula mass

Formula mass is the amount of the masses of the atoms existing in the empirical formula. It is calculated utilizing the unit “amu” (atomic mass units). Each and every atom has a mass offered by amu systems. 1 amu is equal to 1.66 x 10-24 g. Let us think about few examples in order to understand also how to calculate the formula mass.

Ex: The formula mass for MgCl2.

The empirical formula for MgCl2 is the same as the molecular formula. Because of this, the formula mass deserve to be calculated as follows.

The mass of Mg atom = 24.305 amuThe mass of a Cl atom = 35.453 amuAs such the formula mass = (24.305 amu) + (2 x 35.453 amu) = 95.211 amu

Ex: The formula mass of C4H10

The empirical formula for C4H10 is C2H5. Because of this, the formula mass deserve to be calculated as complies with.

The mass of C atom = 12.0107amuThe mass of an H atom = 1.0079 amuAs such the formula mass = (2 x 12.0107amu) + (5 x 1.0079 amu) = 29.0609 amu


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Figure 1: C4H10


Likewise, the worth of the formula mass is periodically equal to the molecular mass, however sometimes it is less than molecular mass. But the formula mass cannot be better than the molecular mass.


What is Molecular Mass

The molecular mass of a molecule is the mass of a mole of that molecule. This suggests it is the sum of the masses of molecules present in a mole. This is calculated utilizing the molecular formula of a molecule. Here, the atomic weights of each atom in g/mol unit are added to gain the molecular mass.

One mole of a molecule is written of 6.023 x 1023 molecules. Therefore, the molecular mass is the weight of 6.023 x 1023 molecules. Due to the fact that the atomic masses of each facet are recognized, it is basic to calculate the molecular mass quite than reasoning of a 6.023 x 1023 of molecules.

Calculation of Molecular Mass

Let us consider some examples.

Ex: Molecular mass of HCl

The atomic weight of H = 1.0079 g/molThe atomic weight of Cl = 35.453 g/molThe molecular mass of HCl = (1.0079 g/mol) + (35.453 g/mol) = 36.4609 g/mol.

Ex: Molecular mass of C3H6

The atomic weight of C = 12.0107 g/molThe atomic weight of H = 1.0079 g/molThe molecular mass of C3H6 = (3 x 12.0107 g/mol) + (6 x 1.0079 g/mol) = 42.0795 g/mol


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Figure 2: C3H6


The molecular mass of a molecule is also dubbed the molar mass. This is because the mass is given per one mole.

Difference Between Formula Mass and also Molecular Mass

Definition

Formula Mass: Formula mass is the amount of the masses of atoms current in the empirical formula.

Molecular Mass: Molecular mass of a molecule is the mass of a mole of that molecule.

Units

Formula Mass: The formula mass is calculated from amu systems.

Molecular Mass: The molecular mass is calculated from g/mol units.

Calculation

Formula Mass: The formula mass is calculated utilizing the empirical formula.

Molecular Mass: The molecular mass is calculated making use of the molecular formula.

Value

Formula Mass: The formula mass may or might not offer the exact mass of a molecule.

Molecular Mass: The molecular mass constantly provide the specific mass of a mole of molecules.

Conclusion

Formula mass and also molecular mass of a molecule deserve to conveniently be calculated utilizing the atomic masses of the atoms that are existing in the molecule. But the formula mass is calculated using the empirical formula whereas the molecular mass is calculated using the actual formula. Sometimes the empirical formula and also the molecular formula are the same for a molecule. Then, the formula mass and molecular mass are the exact same. The major difference between formula mass and the molecular mass is that the formula mass is calculated by adding the masses of atoms present in the easiest formula that have the right to be provided for a molecule whereas the molecular mass is calculated making use of the actual numbers of atoms present in a molecule.

See more: Why Should The Potassium Salts Of Fatty Acids Yield Soft Soaps

References:

1. Helmenstine, Ph.D. Anne Marie. “Resee This Sample Problem to Find Molecular Mass of a Compound.” ThoughtCo, Available here. Accessed 13 Sept. 2017.2. Helmenstine, Ph.D. Anne Marie. “What is the Difference in between Formula Mass and Molecular Mass?” ThoughtCo, Available below. Accessed 13 Sept. 2017.3. “Molar mass.” Wikipedia, Wikimedia Foundation, 23 Aug. 2017, Available here. Accessed 13 Sept. 2017.

Image Courtesy:

1. “Butane-3D-balls” By Ben Mills and also Jynto – Derivative of File:Propan-1-ol-3D-balls.png. (Public Domain) by means of Commons Wikimedia2. “Propylene-3D-balls” By Ben Mills and Jynto – Derivative of File:Cis-but-2-ene-3D-balls.png. (Public Domain) by means of Commons Wikimedia