Molar Mass is defined as the mass in grams of one mole of the given compound. It is also called Molecular Weight.
Let’s learn about molar mass in more detail.
What is Molar Mass?
Molar mass is the mass of one mole of the compound in grams. It is also defined as “mass per mole”. Molar mass is the sum of the mass of atoms in 1 mole of a substance.
Mole is the unit used as a standard value in chemistry, and the standard value of 1 mole of any substance (atoms, molecules, etc.) is 6.023 Ă 10^{23} units.
Molar Mass Unit
The standard unit of molar mass is grams per mole. The molar mass unit is represented as grams/mol. The SI unit of molar mass is kg mol^{1}.
Mole Definition
Mole, also written as mol, is the fundamental unit used to measure the amount of substance. A mole is defined as the amount of substance containing the same number of different entities (such as atoms, ions, molecules, and compounds) as the number of atoms in a sample of pure 12C weighing precisely 12 g.
Even a gram of any pure element contains a high amount of atoms. One mole is also defined as the amount of a substance that contains as many entities as there are atoms in exactly 12 g of the ^{12}C isotope.Â
Molar Mass Formula
We can calculate the mass of atoms, molecules, etc. However, it becomes difficult to calculate the mass of each particle present in the substance.
The following formula is used to calculate molar mass :
Molar Mass of Substance = (Mass of SubstanceÂ in grams)/(Number of Moles of Substance) = g/mol
Below are some of the important formulas regarding molar mass:
Formulas Related to Molar Mass 


Number of Moles of Atom  (Mass of Element in Gram)/(Relative Atomic Mass) 
Number of Moles of Molecules  (Mass of Substance in Gram)/(Relative Molecular Mass) 
Percentage Yield  (Actual mass of Product)/(Theoretical Mass of Product) 
Percentage of Composition  (Mass of Entity present in Substance)/(Total Mass of Substance) 
Mole fraction formula  (Number of Moles of Component in Mixture)/(Total Number of Moles in Component) 
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How To Calculate Molar Mass
The French physicist Jean Baptiste introduced “Avogadro’s number”. Avogadro’s number is present in 1 mole of a substance. The substance can be atoms, molecules, etc.
1 mol = 6.023 Ă 10^{23} units
Molar Mass of Compounds
The molar mass of the compound is the total molar mass of all the atoms present in the compound. It is calculated by taking the individual molar mass of each atom of the compound and adding all of them.Â
Molar Mass of CH_{4}
It is clear from the chemical formula of methane that it has 1 carbon atom and 4 hydrogen atoms.
Thus, the molar mass of Methane is calculated as,
Mass of 4 hydrogen atoms = 4 Ă Mass of 1 Hydrogen atom = 4 Ă 1 = 4 amu
Mass of 1 carbon atom = 1 Ă Mass of 1 Carbon atom = 1 Ă 12 = 12 amu
Molar mass of Methane = 4 + 12 = 16 amu
Now, let’s take a look at some more examples to understand to find the molar mass of molecules,
Molar Mass of H_{2}O
The molar mass of water is the total sum of atomic masses of the atoms, and water (H_{2}O) contains 2 atoms of hydrogen and 1 atom of oxygen. The atomic mass of hydrogen is 1 amu and the atomic mass of oxygen is approximately 16 amu. Therefore, the molar mass of water becomes 18 g/mol.
Molar Mass of CO_{2}
The molar mass of CO_{2} is the total sum of atomic masses of the atoms, and CO_{2} contains 2 atoms of oxygen and 1 atom of carbon. The atomic mass of carbon is 12 amu and the atomic mass of oxygen is approximately 16 amu. Therefore, the molar mass of CO_{2} becomes 44 g/mol.
Molar mass of H_{2}SO_{4}
The chemical formula of Sulfuric Acid is H_{2}SO_{4}. It contains two hydrogen atoms, one sulfur atom and four oxygen atoms. We know that the molecular weight of Hydrogen (H) is 1.0078 g/mol, Sulfur (S) is 32.065 g/mol, and Oxygen (O) is 16 g/mol. Therefore, the molar mass of sodium carbonate is,
 H = 2 Ă 1.0078 = 2.0156 g/mol.
 S = 1 Ă 32.065 = 32.065 g/mol.
 O = 4 Ă 16 = 64 g/mol.
By adding all we get = 2.0156 + 32.065 + 64 = 98.081 g/mol. Therefore, the molar mass of H_{2}SO_{4 }is 98.081 g/mol.
Molar mass of NaOH
The chemical formula of Sodium Hydroxide is NaOH. It has one hydrogen atom, one oxygen atom, and one Sodium atom. We know that the molecular weight of Hydrogen (H) is 1 g/mol, Oxygen (O) is 16 g/mol and Sodium (Na) is 23 g/mol.
Therefore, the molar mass of sodium hydroxide is,
 Na = 1 Ă 23 = 23 g/mol
 O = 1 Ă 16 = 16 g/mol
 H = 1 Ă 1 = 1 g/mol
By adding all we get = 23 + 16 + 1 = 40 g/mol. Therefore, the molar mass of NaOH is 40 g/mol.
Molar mass of NaCl
The chemical formula of Sodium Chloride is NaCl. It has one Sodium atom and one Chlorine atom. We know that the molecular weight of Sodium (Na) is 23 g/mol and Chlorine (Cl) is 35.5 g/mol.
Therefore, the molar mass of sodium chloride is,
 Na = 1 Ă 23 = 23 g/mol
 Cl = 1 Ă 35.5 = 35.5 g/mol
By adding all we get = 23 + 35.5 = 58.5 g/mol. Therefore, the molar mass of NaCl is 58.5 g/mol.
Molar mass of Urea
The chemical formula of Urea is NH_{2}CONH_{2}. It has two Nitrogen atoms, four Hydrogen atoms, one Carbon atom, and one Nitrogen atom. We know that the molecular weight of Nitrogen (N) is 14 g/mol, Hydrogen (H) is 1 g/mol, Carbon (C) is 12 g/mol, and Oxygen (O) is 16 g/mol.
Therefore, the molar mass of Urea is,
 N = 2 Ă 14 = 28 g/mol
 H = 4 Ă 1 = 4 g/mol
 C = 1 Ă 12 = 12 g/mol
 O = 1 Ă 16 = 16 g/mol
By adding all we get = 28 + 4 + 12 + 16 = 60 g/mol. Therefore, the molar mass of Urea is 60 g/mol.
What is Percentage of Composition?
Percentage of Composition refers to the proportion or distribution of different components within a mixture or a compound. It is used to express the relative amount or concentration of each component as a percentage of the total.
The percentage of composition of any compound is calculated by following the steps given below,
Step 1: Find the molar mass of the substance (atom) for which we have to find the percentage composition.
Step 2: Find the molar mass of the given substance.
Step 3: Calculate the percentage of the composition by using the formula,
Percentage = (Mass of Substance / Mass of Compound) Ă 100
Example: Find the mass percentage of hydrogen in a water molecule.
Solution:
Chemical Formula of Water = H_{2}O
Thus, water has 2 hydrogen atoms and 1 oxygen atom
Mass of 2 hydrogen atoms in 1 mole of water = 2 Ă Mass of Hydrogen atom = 2 Ă 1 = 2 g
Mass of 1 mole of water molecule = 2 Ă Mass of Hydrogen atom + 1 Ă Mass of Oxygen atom
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 2 Ă 1 + 1 Ă 16 = 18 g
Mass Percentage of Hydrogen in Water = 2 / 18 Ă 100 = 11.11 %
Molar Mass of Various Compounds
The molar mass of some compounds is discussed in the following table,
Compounds 
Chemical Formula 
Molar Mass 

Urea  CH_{4}N_{2}O  60.06 g/mol 
Sulphur  S  32.065 g/mol 
Oxygen  O  15.99 g/mol 
Oxalic Acid  C_{2}H_{2}O_{4}  90.03 g/mol 
Aluminium  Al  26.981 g/mol 
Carbon  C  12.011 g/mol 
Hydrogen  H  1.007 g/mol 
Sodium  Na  22.989 g/mol 
Calcium  Ca  40.078 g/mol 
Copper  Cu  63.546 g/mol 
Iron  Fe  55.845 g/mol 
Helium  He  4.002 g/mol 
Iodine  I  126.904 g/mol 
Oxygen Gas (O_{2})  O_{2}  15.999 g/mol 
Chlorine  Cl  35.453 g/mol 
Hydrogen Gas (H_{2})  H_{2}  2.016 g/mol 
Phosphorus  P  30.973 g/mol 
Benzene  C_{6}H_{6}  78.11 g/mol 
Methane  CH_{4}  16.04 g/mol 
Sodium Carbonate  Na_{2}CO_{3}  105.988 g/mol 
Acetic Acid  CH_{3}COOH  60.052 g/mol 
Calcium Carbonate  CaCO_{3}  100.086 g/mol 
Ethanol  C_{2}H_{5}OH  46.07 g/mol 
Sucrose  C_{12}H_{22}O_{11}  342.3 g/mol 
Related :
Solved Examples on Molar Mass
Example 1: Find the molar mass of Sodium Carbonate(Na_{2}CO_{3}).
Solution:Â
The chemical formula of Sodium Carbonate is Na_{2}CO_{3}. It contains two sodium atoms, one carbon atom and three oxygen atoms. We know that the molecular weight of Sodium (Na) is 22.98g/mol, Carbon (C) is 12.011 g/mol and Oxygen (O) is 16 g/mol. Therefore, the molar mass of sodium carbonate is
 Na = 2 Ă 22.98 = 45.96 g/mol
 C = 1 Ă 12.011 = 12.011 g/mol
 O = 3 Ă 16 = 48 g/mol
Molecular Weight of Na_{2}CO_{3 }= 45.96 + 12.011 + 48Â
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 105.971 amuTherefore, the molar mass of Na_{2}CO_{3} is 105.971 g/mol.
Example 2: Find the molar mass of hydrochloric Acid (HCl).
Solution:
The chemical formula of Hydrochloric acid is HCl. It contains one Hydrogen atom, one chlorine atom. We know that the molecular weight of Hydrogen (H) is 1.0078g/mol, Chlorine (Cl) is 35.453 g/mol. Therefore, the molar mass of hydrochloric acid is
 H = 1 Ă 1.0078 = 1.0078 g/mol
 Cl = 1 Ă 35.453 = 35.453g/mol
Molecular Weight of HCl = 1.0078 + 35.543Â
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 36.460 g/molTherefore, the molar mass of HCl is 36.460 g/mol.
Example 3: Find the molar mass of Glucose (C_{6}H_{11}O_{6}).
Solution:
The chemical formula of Glucose is C_{6}H_{11}O_{6}. It contains six carbon atoms, eleven hydrogen atoms and six oxygen atoms. We know that the molecular weight of Carbon (C) is 12.011 g/mol, Hydrogen (H) is 1.0078 g/mol and Oxygen (O) is 16 g/mol. Therefore, the molar mass of glucose is,
 C = 6 Ă 12.011 = 72.066 g/mol.
 H = 12 Ă 1.0078 = 12.094 g/mol.
 O = 6 Ă 16 = 96 g/mol.
Molecular Weight of C_{6}H_{11}O_{6 }= 72.066 + 12.094 + 96
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 180.16 g/mol.ÂTherefore, the molar mass of Glucose is 180.16 g/mol.
FAQs on Molar Mass
What is Molar Mass?
The molar mass of the compound is defined as the mass of one mole of a compound measured in grams. It is calculated in g/mol.Â
Are Molar Mass and Molecular Mass the same?
No, molar mass and molecular mass are not the same. Molar mass is the mass of one mole of the substance, which is measured in grams and molecular mass is the mass of one molecule and is measured in AMU.
Why is Avogadro’s Number called a Mole?
The mole (mol) is a unit that is equal to Avogadro’s number. The word ‘mole’ has come from the word molecule. 1 mole of any substance is equal to 6.023 Ă 10^{23 }units, which is the Avogadro’s number. For example, 1 mole of water molecule contains 6.023 Ă 10^{23} molecules.
What is Avogadro’s Law?
Avogadro’s law or the theory of Avogadro is an experimental law which is related to the volume of gas w.r.t the amount of gas. Avogadro’s law states “equal quantities of all gases have same number of molecules at the same temperature and pressure”.
What is One Mole Equal To?
One mole is the collection of 6.0221367 ĂÂ 10^{23} units of a substance. Here, the substance is atoms, molecules, or ions.
What is Molar Mass of Fluorine?
The molar mass of fluorine (Fâ), which is the diatomic form of the element, is approximately 38.00 grams per mole (g/mol).
What is Molar Mass of Benzene?
Molar mass of Benzene is approximately 72.06 grams per mole (g/mol)