Key Difference – Formula Mass vs Molar Mass  

Formula mass and also molar mass are two physical properties of molecules that display some distinction between them. Both of these parameters, the formula mass and also molar mass, are pertained to the weight of chemical elements (atoms, molecules, unit cells). Due to the fact that atoms, molecules, and also unit cells are very small particles; the mass of one ppost is negligibly tiny. Because of this, the mass of 1mol (mass of 6.02 * 1023 pposts in grams) is offered as the unit in quantitative analysis. Different chemical facets have various molar mass values (C -12.01 g mol-1, Mg-24.3050 g mol-1) because they have a different variety of positions in the nucleus. Similarly, this leads to having actually various unique molar mass values for chemical compounds (NaCl–58.4426 g mol-1). Formula mass is calculated considering the empirical formula of a compound. It is the amount of the atomic mass values of individual components in the empirical formula (H2O-18.00 g mol-1). The crucial difference between formula mass and also molar mass is that, the formula mass of a molecule or a compound is the amount of the atomic weights of the atoms in its empirical formula while molar mass is the mass in grams of 1 mol of substance.

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What is Formula Mass?

The formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in the empirical formula. The units of formula mass “atomic mass unit” (amu).

Formula Mass Calculation

Example 1:

What is the formula mass of NaCl (Atomic mass of Na = 22.9898 amu, Atomic mass of Cl = 35.4527 amu)?

Formula mass of NaCl = Na + Cl

= 22.9898 amu + 35.4527 amu

= 58.4425 amu

Example 2:

What is the formula mass of C2H5OH (C = 12.011 amu, H = 1.00794 amu, O – 15.9994 amu)?

Formula mass of C2H5OH = 2C + 6H + O

= 2(12.011 amu) + 6 (1.00794 amu) + (15.9994 amu)

= 46 amu

What is Molar Mass?

 Molar mass is defined as the mass of 1mol of substance. It has actually the systems of g/mol or kg/mol. Eextremely chemical facet or chemical compound has actually a unique value for molar mass.

Molar mass = Mass of one pwrite-up * (NA – Avogadro’s constant)

NA = 6.022 * 1023mol-1

Molar Mass of Elements

Different facets have a distinct molar mass value bereason they contain various numbers of electrons, protons, and also neutrons. For instance,

Molar mass of Carbon is 12.01 g mol-1.

Molar mass of Magnesium is 24.3050 g mol-1.

Molar Mass of Molecules and Compounds

The molar mass of water (H2O) is 18.00 g mol-1

The molar mass of Mg(OH)2 is 58.3197 g mol-1

1 mol ofNumber of particlesMolar mass
C (element)6.022 * 1023 atoms12.011 g mol-1
Cu (element)6.022 * 1023 atoms63.546 g mol-1
Fe2O3 (ionic compound)6.022 * 1023 unit cells159.70 g mol-1
Al(OH)3 (ionic compound)6.022 * 1023 unit cells78.00 g mol-1
CF4 (covalent compound)6.022 * 1023 molecules88.01 g mol-1
N2O5 (covalent compound)6.022 * 1023 molecules108.011 g mol-1
SiO2 (covalent compound)6.022 * 1023 molecules60.09 g mol-1

What is the difference between Formula Mass and also Molar Mass?

Definition of Formula Mass and also Molar Mass

Formula Mass: The formula mass (formula weight) of a molecule is the sum of the atomic weights of the atoms in its empirical formula.

Molar Mass: Molar mass is the mass in grams of 1 mol of substance (The variety of pwrite-ups in a mole is equal to 6.022 * 1023).  


Formula mass: Formula mass is calculated for chemical compounds. It is calculated making use of the empirical formula.

Molar mass: Molar mass is calculated for chemical substances that contain many type of elementary entities such as chemical facets, ionic and also covalent chemical compounds.

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Basis of Calculation

Formula mass: Different chemical aspects in the chemical compounds offer different formula masses.

Molar masses: Different atomic masses lead to distinctions in molar masses. The atomic mass of an aspect (in atomic mass units – amu) is equal to its “molar mass”