What is Molar Mass?
In simple terms, molar mass is defined as 'mass per mole.' That is in other word we can say that- Molar mass is the addition of the mass of all the atoms in one mole's worth of a substance. Unit of molar mass is grams per mole (g/mol).
Molar mass is represented for elements or molecules. In the case of single elements or individual atoms, the molar mass would just be the element's mass expressed in atomic mass units. In other words, the atomic mass and the molar mass of an individual atom are exactly equal. As molar mass and atomic mass are equal for individual atoms, molar mass can be used to measure the particle's identity. For example, the atomic mass of He is 4. Helium is found as monoatomic in nature, meaning that it has only one atom, so its molar mass is also 4.
When individual atoms are bonded to form a molecule, the molar mass represents the mass of all the atoms. Molar mass is different from molecular mass in that molecular mass is the mass of a given molecule, whereas molar mass is the mass of one mole of the given molecule.
Molar Mass Formula:
The molar mass formula is used to show the molar mass of a substance is as follows:
In this above formula, molar mass is represented in units of g/mol.
>To determine the molar mass of a substance, following steps are useful.
Step 1: Follow the perfect formula of the compound to determine the elements present.
Step 2: Determine the total number of atoms for each element.
Step 3: From the periodic table to determine the atomic mass of every element in the compound.
Step 4: Multiply the number of atoms of an element times the atomic mass of one atom of that element. Do this for every unique element in the compound.
Step 5: Adds this values for the molar mass in the gram/mol unit.
If we have mass and we want to calculate number of moles i.e To convert a given mass into a mole, divide the mass by the molar mass. And if we have moles and we want to calculate mass i.e To convert the given mole into mass, multiply the mole by the molar mass. For the calculation of the molar mass of a given compound, find the addition of the atomic masses of all of the atoms of a molecule.
Examples of Molar mass calcations:
1) What is the molar mass of sodium carbonate, Na2CO3 ?
Sodium carbonate contains two atoms sodium, one atom of carbon and three atoms of oxygen. The molecular weight would be
Na : (2 x 23.0 g) = 46g
C : (1 x 12.0 g)= 12g
O : (3 x 16 g) =48g
When we add up the total values.
46 + 12 + 48 = 106 g/mol.
Therefore, the molar mass of Na2CO3 is 106 g/mol.
2) What is the molar mass of calcium nitrate, Ca(NO3)2 ?
In calcium nitrate contains one atom of calcium, two atoms of nitrogen and six atoms of oxygen.
Ca: (1 x 40.1g) = 40.1g
N: (2 x 14.0g) = 28g
O: (6 x 16.0g) = 96g
If we add all, (40.1 + 14 + 16)=
164.1 g/mol
Therefore, the molar mass of Ca(NO3)2 is 164.1 g/mol.
3) What is the molar mass of HNO3:
HNO3 the formula for nitric acid:
H : (1× 1.0 g)= 1.0g
N : (1× 14.0g) = 14g
O : (3×16.0g) = 48g
Molar mass of HNO3 = (1+14 +48)= 63.0 g/ mole
Molar mass of HNO3 = 63.0 g/mol.
4) What is molar mass of H2O:
The are two atoms of hydrogens and one oxygen atom.
H : (2×1g) = 2g
O: (1×16g) = 16g
Total molar mass of H2O= (2+16)=18g/mol.
5) What us Molar mass of H2SO4:
In sulfuric acid, there are 2 hydrogen atoms, one sulphur atom, and four oxygen atoms.
Molar mass = Molar mass [2(H)+S+4(O)]
H : (2×1.00g) = 2 g
S : (1×32g)= 32 g
O : (4×16g) = 64g
If we add all, (2+32+64)= 98 g/mol
Hence, the molecular mass of h2so4 is 98g/mol.
6) Calculate the molar mass of Benzene (C6H6):
In Benzene, there are 6 carbon atoms and 6 hydrogen atoms.
C: (6×12.0g)= 72g
H: ( 6× 1.00g)= 6 g
If we add all, (72+6)= 78g/mol.
7) Calculate the molar mass of NaCl:
In NaCl there are two ions: Na+ and Cl-
Na: (1×23g)= 23g
Cl: (1× 35g) = 35g
Add both masses, we get (22+35)= 58g/mol
8) Calculate the molar mass of NaOH:
In NaOH, there are three atoms Sodium, oxygen and hydrogen.
Na: (1× 23g)= 23g
O: (1×16g) =16 g
H: (1× 1.00g)= 1.00g
Add this values, we get
(23+16+1.00)= 40g/mol.
So, like above examples we can calculate the many different types of molecules molar masses.
