Mole Concept

• Scientists do not only measure substances by weight or volume. In some instances, they also measure the number of particles in a substance.


  Counting atoms, molecules, or ions, on the other hand, is not that simple due to their very small size.
• The mole represents a specific number of particles just like a dozen eggs would refer to twelve eggs, etc.


  A mole is defined as the number of particles present in exactly 12 grams of carbon-12.
• Atom, molecule, and ion are particles.


  One mole of any substance consist of 6.02x10^23 particles.
• 6.02X10^23 is called Avogrado's number or (N subscript A)


  Amedeo Avogrado was the first to propose that the volume of a gas at a given pressure and temperature is proportional to the atoms or molecules regardless of the nature of the gas.
• The development of the atomic theory led to the simple view of the atoms as having protons, electrons, and neutrons.


  The protons and neutrons are in the nucleus, while the electrons are found outside the nucleus.
• The mass of an atom depends mainly on the number of protons and neutrons inside the nucleus since the mass of the electron is very small.


  The mass of electrons is 9.1093897x10^-28.
• The mass of protons is 1.672623x10^-24.


  The mass of neutrons 1.67495x10^-24.
• Amedeo Avogrado is an Italian scientist.


  The mass can be expressed in atomic mass unit (amu) instead of grams, which is a more convenient way of expressing very small masses.
• One amu is equivalent to 1.66054x10^-24 gram.


  The mass of the proton and neutron is approximately 1 amu.
• Atoms are made up of protons, electrons, and neutrons.


  The mass of the electron is so small that it does not contribute to the mass of the atom.
• Helium contains two protons, two neutrons, and two electrons.


  The mass of an atom can be expressed in atomic mass unit.
• One amu is equivalent to 1/12 of the mass of a carbon-12 isotope.


  Like atomic mass, molecular and formula mass are the relative mass of the carbon-12 isotope as standard.
• The atomic mass unit is also known as the unified atomic mass unit and Dalton.


  The symbol is unified atomic mass unit is u.
• The symbol is Dalton is D.


  The molecular mass is simply the sum of the masses of the atoms in the molecule of the substance.
• One mole of a substance consists of 6.02x10^23 particles of that substance.


  When carbon burns, one mole of carbon atoms reacts completely with one mole of oxygen molecules.
• The mass in grams of one mole of a substance is called molar mass.


  The unit for molar mass is grams per mole.
• The symbol of grams per mole is g/mol.


  The molar mass is the mass equivalent to one mole of a substance.
• The amount of matter can be expressed in three different ways: mass in grams, number of particles, and mole.


  Conversion from mass to mole, mole to the number of particles and vice versa can be easily determined using dimensional analysis.
• The goal in dimensional analysis is to cancel out units other than the desired units through the use of fixed relationships.


  Fixed relationships can be written in ratio or fraction and is also called as conversion factors.
• The expanded form of 6.02x10^23 is 602,000,000,000,000,000,000,000.


  We use the unit mole to count the molecules.
• Mole represents the number of particles present in exactly 12 grams of carbon-12.


  One mole of something is equal to 6.02x10^23.
• Atomic theory states that atoms are made of protons and neutrons in the nucleus and electrons outside the nucleus.


  For ionic compounds, the term molecular mass is inappropriate since they are composed of charged particles or ions. There are NO MOLECULES in ionic compounds.
• The mass in amu of one atom or molecule is molecular mass.


  The mass in grams of one mole of a substance is molar mass.
• Molar mass is numerically equal with atomic mass (amu).


  Similarly, molar mass of a molecule is numerically equal with its molecular mass.