What is Molecular Mass?
It is the sum of atomic mass of all the atoms in a molecule
Example - Molecular Mass of H 2 O
- Atomic Mass of Hydrogen (H) =1 u
- Atomic Mass of Oxygen (O) =16 u
- Molecular Mass of Water (H 2 O) = 2*1+16*1 = 2 + 16 = 18 u
Example - Molecular Mass of HNO 3
- Atomic Mass of Hydrogen (H) =1 u
- Atomic Mass of Nitrogen (N) =14 u
- Atomic Mass of Oxygen (O) =16 u
- Molecular Mass of Nitric Acid (HNO 3 ) = 1 *1+ 14*1+ 16*3 = 1+14 + 48 = 63 u
A few more examples of Molecular masses are:
What is a Molecule?
A group of atoms chemically bonded together is Here are the valency of a few elements:
called Molecule.
What is Formula Unit Mass?
It is sum of atomic mass of all atoms in formula unit of compound
It is calculated in same manner as Molecular Mass
Only difference is it is used for those substances whose constituent element is ions
(it is used for ionic compounds)
What is a Molecule?
A group of atoms chemically bonded together is Here are the valency of a few elements:
called Molecule.
Example 1
Sodium Chloride (NaCl) contains 2 ions, Positively charged Sodium ions (Na+) and Negatively charged Chloride Ions
Formula Unit Mass of Sodium Chloride
Atomic Mass of Sodium (Na) = 23 u
Atomic Mass of Chloride (Cl)= 35.5 u
Formula Unit Mass of Sodium Chloride = 23*1+ 35.5*1 = 23+35.5 = 58.5 u
What is a Molecule?
A group of atoms chemically bonded together is Here are the valency of a few elements:
called Molecule.
Example 2
Calcium Chloride ( CaCl 2 ) contains 2 IONS, Positively charged Calcium ions (Ca +2 ) and Negatively charged Chloride (2 Cl -1 ) Ions
Formula Unit Mass of Calcium Chloride
Atomic Mass of Calcium (Ca) = 40 u
Atomic Mass of Chloride (Cl)= 35.5 u
Formula Unit Mass of Calcium Chloride (CaCl 2 ) = 40*1 + 35.5*2 = 40+71 = 111 u
What is a Molecule?
A group of atoms chemically bonded together is Here are the valency of a few elements:
called Molecule.
Comparison between Atomic Mass, Molecular Mass and Formula Unit Mass
|
Atomic Mass |
Molecular Mass |
Formula Unit Mass |
|
It is the mass of an atom of a chemical element |
It is the Sum of Atomic Masses of all the atoms in a molecule |
It is sum of atomic mass of all atoms in formula unit of compound |
|
It is used to measure mass of a single atom |
It is used to measure mass of a single molecule |
It is used to measure mass of those substances whose constituent elements are ions |
What is a Molecule?
A group of atoms chemically bonded together is Here are the valency of a few elements:
called Molecule.
|
Atomic Mass of Hydrogen = 1 u |
Molecular Mass of Water (H 2 O) = (2x1) +(16x1) =2+1= 18 u |
Formula Unit Mass of Sodium Chloride (NaCl) = (23x1) + (35.5x1) =23+35.5 = 58.5 u |
Example - 3.1,3.2
In text Question - Page 40 Q1,Q2
NCERT Question -
