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Lecturer. S.Fayyaz Hussain
City Of Knowledge
(Science Campus)
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INTRODUCTION
TO CHEMISTRY
Chemistry:
Chemistry is a branch of science which deals with nature
composition properties and structure of matter.
Element:
“An element is the simplest form of matter which can not
further convert into simpler one”.
Example Iron, Copper, Oxygen, Gold, Silver, Carbon.
“An element is the
collection of atoms having same atomic number”.
Compound:
Compound are pure
substance composed of two or more elements combined chemically in fixed ratio.
For example sodium
chloride is composed of sodium and chlorine and in it there is always 39.34%
sodium and 60.66% chlorine.
Mixture:
A mixture is a mixed
substance composed of two or more pure substance.
Atom:
Matter is composed of
very very small particles called atom.
An atom is the fundamental unit of an element; it represents all the
properties of an element. An atom is small entities which can take part in
chemical reaction.
Molecules:
A molecule is a
particle of matter which can exist in Free State.
A molecules is the
fundamental unit of an element or compound
For Example.
O2 Is a molecule of oxygen element.
CO2 is a molecule of carbon dioxide (carbon
dioxide is a compound)
Atomic Mass:
The mass of an atom of
an element is known as the atomic mass.
An atom is extremely small particles. Thus the atomic masses are not
expressed in gram, kilo gram, milligram and micro gram, it is expressed in very
small unit called the atomic mass unit (a.m.u.)
1 a.m.u. = mass
of one atom of C – 12 x 1
12
The atomic mass of an
element is the relative average mass of that element which is determined by compare
with C – 12. Thus The atomic mass of an element tells how
much heavier or lighter is that element as compared to C – 12.
Molecular Mass:
The
mass of the molecule is known as molecular mass.
“The molecular mass of molecules is the sum of atomic
of all the atoms present in that molecule”.
Molecular
Formula:
Molecular
formula of a compound is the formula which shows the exact number of atoms of
different elements present in molecule of that compound.
For Example:
The molecular formula of glucose C6H12O6
Some elements occur naturally in molecular form. They are represented by
molecular formula
e.g. N2 O2 Cl2 and
H2
Empirical
Formula:
Empirical
formula of a compound is the formula which shows the simplest ration between
the numbers of atoms of different elements present in that compound.
It is also known as simplest formula.
e.g. The
empirical formula of glucose CH2O
Mole:
“A mole is the amount of any substance that contain as
many atoms or molecules, or formula unit as there are atoms in 12g of carbon
–12”
(OR)
“The amount of
substance which contains 6-02 x 1023 (Avogadro’s number) atoms or molecules
is called a mole”We can define a mole another way as well.
“A mole is the
atomic mass, (OR) molecular mass or formula mass any substance expressed in
grams”
(The above
definition is explained mole as quantity. This definition is gram equivalent of
mole.)
Avogadro’s Number:
It has been
experimentally found that one mole of any substance contains a constant number
of particles which is equal 6-02 x 1023 . It is represented by N
Determination of Empirical Formula:
Empirical formula can be
determined as follows:
1) Identification of elements:
First of all the given
unknown compound is subjected to quantitative analysis. To identify which
elements are present in the compound.
2) Determination of mass of element:
Determine the mass of each
element present in particular amount of sample.
3) Determination the percentage of composition of
compound:
Determined the amount OR
mass of each elements in 100g of given compound.
4) Calculation of mole ratio:
Percentage of elements are
divided by their respective atomic masses to find out the ratio of moles of
atoms of the element.
5) Conversion:
Conversion of moralities
into small whole numbers by dividing each by the smallest of the number.
This will give the simplest
ratio of atoms of different element in the given compound.
Determination of Molecular Formula:
Molecular formula of compound is the integral multiple of its empirical
formula.
Molecular formulas =( Empirical
formula)n
(n = 1,2,3……)
n can be determined as
n = Molecular
formula mass
Empirical formula mass
STOICHIOMETRY
Definition:
The branch of chemistry which deals with quantitative relation ships
between reactants and product in a balanced chemical equation is called Stoichiometry.
Stoichiometric Reaction:
The mole ratio in
which the reactant combine together with the mole ratio in which products are
formed is called Stoichiometric reaction.
Stoichiometric Amount:
In a balanced chemical
equation the amount of reactants and products are called Stoichiometric
amounts.
e.g. C
+ O2 CO2
12g
32g 44g
12g, 32g and 44g are called stoichiometric amount in this reaction.
Stoichiometric Calculation:
The calculations based on
stoichiometric are called stoichiometric calculation.
Assumption for Stoichiometric Calculation:
To perform stoichiometric
calculation following assumption are necessary.
I )
All the reactant
are completely convert in to product.
No
side reaction is taking place
II )
Law of
conservation of mass and law of definite proportions are
obeyed.
Law Employed in Stoichiometry:
Whenever
we do the stoichiometric calculation, two raws are to be considered.
I )
Law of conservation
of mass
II )
Law of definite
proportion of mass
Relation Ships of Stoichiometric
Calculation:
There are types of relation ships
that we have to face, during these calculation.
- Mass – Mass relationships
- Mass – Volume relationships
- Volume – Volume relationships
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