Molar mass, molecular mass and mole concept
The matter all around us are composed of atoms, the mass of the matter is one of the properties of the matter, it is the property which is determined by the some of the fundamental particles of the atom, the fundamental particles protons and neutrons are the contributor of the atomic mass, molecular mass or molar mass, although according to current theory protons and neutrons are also composed of quarks which is the smallest fundamental particle of the atom, so quarks are the basic contributors to add mass to atomic mass, molecular mass or molar mass, electrons are transformed from the leptons which is also known as basic fundamental particle but leptons are unstable particles,so quarks, electrons, and leptons are one of the basic fundamental particles, recently one more particle Hibbs boson is also discovered to have existed, this particle is the cause of the existence of the mass in the universe. Hibbs boson is an unstable particle and breaks down into the quarks. Hibbs boson is the generator of quarks which add mass to atomic mass, molecular mass or molar mass so scientist has called it God particle. All of these similar particles you can study in higher classes in particle physics theory. Here we shall study the theory based on the subject curriculum of middle-class students only.
Before we study what is mole concept, molecular mass, molar mass, first we are required to study the atomic mass of an element.
Before we study molar mass, molecular mass and mole concept we need to clarify what is atomic mass.
The number of protons in the nucleus is known as the atomic number which indicates the identity of an element because it is the total positive charge of the atom which is equal to the total number of negatively charged electrons. Electrons revolve around the nucleus almost with the speed of light so electrons do not contribute to adding mass to the atom. The protons and neutrons are called nucleons of the atoms, the mass of each single nucleons is known as 1 atomic mass unit, if total number of nucleons is 16 then the atomic mass is equal to the product of 16 and 1amu means 16 amu.
The molecule is composed of similar or different atoms, so molecular mass is the sum of all the atoms in a molecule, as an example
The molecular mass of is = number of Ca atoms × atomic mass of Ca + number of oxygen atoms × atomic mass of oxygen + number of hydrogen atom× atomic mass of hydrogen
The molecular mass of = 1×40 + 2× 16 +2×1=40 + 32 + 2 =74 amu
Hence the molecular mass of the is 74 amu.
See the video
As 1 dozen of everything contain 12 things or 1 kg of identical things contain same number of thing on the same way the number of particles(atoms, molecules, ions, protons, neutrons, electrons, etc) in gram equivalent of atomic mass or molecular mass of the particular elements or compounds is fixed in STP(Standard Temperature and Pressure) is fixed. The Avagadro have evaluated this as which is known as Avogadro number or Avagadro constant, it is known as particles in 1 mole of the substance.
Gram equivalent of atomic mass or molecular mass of the particular elements or compounds is known as molar mass, its SI unit is gram. The molar mass of an element or compound contains 1 mole of substance which is equal to the Avogadro number.
Where m =given mass, M = Molar mass, = Avagadro number
Example- Determine the number of moles in 88 gm of .
Answer- The number of moles(n) = where m is given mass and M is the Molar mass of the substance.
Molecular mass of = 12×1 + 16 × 2 = 44 amu
Molecular mass(M) of = 44 gm
Therefore the number of moles in 88 gm are 2 mol.
Example- How many numbers of molecules of water available in 180 gm of water.
Answer. The molecular mass of = 2× 1 + 16 ×1 = 18 u
Molar mass (M) of = 18 gm
The given maa(m) = 180 gm
Therefore the number of molecules of water in 180 gm of water is
Example. How many oxygen atoms are in 1.32 kg of carbon dioxide.
Answer. The molecular formula of carbon dioxide is
The molecular mass of = 12 × 1 + 16× 2= 44 u
The molar mass of carbon dioxide (M) = 44 gm
The given mass of carbon dioxide = 1.32 kg = 1320 gm
The number of molecules of carbon dioxide in 1.32 kg carbon dioxide are
In one molecule of carbon dioxide contain= 2 atoms of oxygen
Number of oxygen atoms in 1.32 kg of carbon dioxide =
Study important questions for your cbse board exams 2020 with their solutions