engineering chemistry Flashcards
Define isotope
Atoms of the same element having different atomic number but the same mass number
Define isobars
Atoms of different elements having the same mass number but different atomic number
Mass number
Protons + neutrons in the nucleus of an atom
Atomic number
Number of protons in the nucleus of an atom.
Number of electrons revolving around the nucleus of an atom.
Charge of a cation
Positive
Charge of an anion
Negative
When electron is transferred from sodium atom to chlorine atom the sodium atom becomes
Cation
The chlorine atom gains an electron hence becomes,
An anion
Oxidation
Process that involves the loss of electrons.
Eg;
Na loses an electron(e-) to become a cation Na+.
Reduction
A process that involves gaining/addition of an electron.
Eg; Cl gains an electron to become an anion Cl-
Octet theory
All the elements with an unstable or incomplete electronic configuration have a tendency to attain the stable electronic configuration of the nearest inert gas configuration either by complete transfer of valence electron from one atom to another or by mutual sharing of valence electron between the atoms
Covalent bond
Formed when a pair of electrons is shared between two atom: Ammonia (NH3)
Ionic/ Electrovalent bond
Complete transfer of one or more electrons from one atom to another
Molecule
A Molecule is the smallest particle of matter(element or a compound)
that can exit freely.
Homoatomic molecule
The molecule is made up of two or more atoms of the same elements.
Molecules of Chlorine(Cl2), Oxygen(O2), and Hydrogen(H2) contain only
two atoms of same kind. So they are called as Homoatomic molecules.
Heteroatomic molecules
The molecule is made up of more than two of more atoms of different
elements.
MOLECULAR MASS:
Molecular mass of an element or a compound is the ratio between the
mass of one molecule of the element or the compound and the mass of 1/12
part of a carbon Atom.
Molecular
Mass of an element or compound = Mass of one molecule of an
Element ÷ 1/12 part by mass of carbon
Mole
The mole is a unit of measurement used in chemistry to
express amounts of a chemical substance. One mole of any substance
contains Avogadro number of particles i.e.,6.023X10^23 particles.
AVOGADRO’S HYPOTHESIS
Avogadro’s Hypothesis states that, “Equal volumes of all gases contain the
same number of molecules at the same temperature and pressure”
Relationship between Molecular Mass & Vapour Density
Vapour Density of a gas is the ratio between the mass of certain volume of
the gas & the mass of the same volume of hydrogen at the same temperature
and pressure.
AVOGADRO NUMBER
one molecular mass (i.e. one mole) of every gas occupies 22.4
litres at S.T.P.
according to Avogadro’s hypothesis equal volumes of all gases at
S.T.P contain equal number of molecules.
Hence it follows that 1 mole of every gas contains the same number of
molecules. This number is called the Avogadro’s number or Avogadro’s
Constant. It is denoted by N. It has been found to be equal to 6.023 x 1023. It
can be defined as “the number of atoms or molecules present in one
mole of an element or a compound respectively”.
Acids
An acid is a substance that gives hydrogen ions (H+
) by itself or in
aqueous solution.
Bases
A base is a substance that gives ions (OH-
) by itself or in aqueous solution.
THEORIES OF ACIDS AND BASES
By the following theories, the acidic and basic nature of substances can be
easily explained
1. Arrhenius theory
2.Lowry-Bronsted theory
3.Lewis theory.
Arrhenius Theory (1827)
Arrhenius Theory (1827)
According to this theory, an acid is a substance that gives hydrogen (H+) ions in water or in aqueous solution.
HCl gives H+ in water, hence it is called as acid.
A Base is a substance that gives hydroxyl ions in water or in aqueous solution
NaOH gives OH– in water; hence, it is called as base.
Strength of an acid (or) base depends upon the extent to produce H+ (or) OH– during ionization.
