Chemical Reactions and Equations
What is Chemical Reaction ?
A chemical reaction is in which the bonds are broken within reactant molecules ,
and
new bonds are
formed within product molecules in order to
form a new substance .
How to know if Chemical Reaction has taken place ? (MBF Er ?)
These type of observations help to determine wheter chemical reaction has taken
us a
place
-
•
change in state
•
change in colour
•
change in temperature
evolution
gas of a
•
formation of precipitate
•
chemical Equation
The simplest to write
equation this in the
equation
way
an is
form a word -
Oxide
Magnesium + Oxide →
Magnesium
( Reactants) (
Product )
Chemical equations can be made more concise and useful if we use chemical
formulae instead
of words .
Mg t Oz → MgO
Magnesium -1 Oxide Magnesium
Oxide
, Balancing a chemical
equation
Fet H2O →
Fez Og + H'z → Lets balance this !
Element Number of atoms in Number of atoms in
reactants ( LHS) products ( RHS )
"
,
Fe 9
'
3
H 2 2
O 9 4
* It is
often convenient to start
balancing with the compound that contain
the maximum number atoms
of .
To balance the atoms
oxygen
-
Atoms of In reactants In products
Oxygen
1) Initial 9 (in H2O) 4 ( in Fez Oa )
) To balance
ii
9×4 4
To balance the atoms
oxygen
-
Fe +4 H2O →
Fez Ou t Hz
, To the number
equalise of H atoms make ,
the number
of molecules
of
molecules RHS
of hydrogen as
four on the .
Atoms Of hydrogen In reactants In products
1) Initial 8 (in 41120) 21in He )
ii) To balance
8 2×4
Fe t 4 H2O → Fez Out 4 He
Examine the above equation and
pick up the third element which is not
balanced .
Find that
only one element is
left to be balanced that
,
is ,
iron .
Atoms iron In In
of reactants
products
1) Initial 9 ( in Fe) 3 Cin Fez Oa )
ii) To balance 9×3 3
3. Fe t 4h20 →
Fez Oat 4th
Writing Symbols of Physical State :
To make chemical informative the
equation physical States of the reactan
•
a more ,
and products with their
are mentioned
along chemical
formulae .
reactants
gaseous liquid aqueous and
The solid States
of and
products are
•
, ,
represented by the notations ( g ) Cl) , ,
Cs) and Cag) respectively .
What is Chemical Reaction ?
A chemical reaction is in which the bonds are broken within reactant molecules ,
and
new bonds are
formed within product molecules in order to
form a new substance .
How to know if Chemical Reaction has taken place ? (MBF Er ?)
These type of observations help to determine wheter chemical reaction has taken
us a
place
-
•
change in state
•
change in colour
•
change in temperature
evolution
gas of a
•
formation of precipitate
•
chemical Equation
The simplest to write
equation this in the
equation
way
an is
form a word -
Oxide
Magnesium + Oxide →
Magnesium
( Reactants) (
Product )
Chemical equations can be made more concise and useful if we use chemical
formulae instead
of words .
Mg t Oz → MgO
Magnesium -1 Oxide Magnesium
Oxide
, Balancing a chemical
equation
Fet H2O →
Fez Og + H'z → Lets balance this !
Element Number of atoms in Number of atoms in
reactants ( LHS) products ( RHS )
"
,
Fe 9
'
3
H 2 2
O 9 4
* It is
often convenient to start
balancing with the compound that contain
the maximum number atoms
of .
To balance the atoms
oxygen
-
Atoms of In reactants In products
Oxygen
1) Initial 9 (in H2O) 4 ( in Fez Oa )
) To balance
ii
9×4 4
To balance the atoms
oxygen
-
Fe +4 H2O →
Fez Ou t Hz
, To the number
equalise of H atoms make ,
the number
of molecules
of
molecules RHS
of hydrogen as
four on the .
Atoms Of hydrogen In reactants In products
1) Initial 8 (in 41120) 21in He )
ii) To balance
8 2×4
Fe t 4 H2O → Fez Out 4 He
Examine the above equation and
pick up the third element which is not
balanced .
Find that
only one element is
left to be balanced that
,
is ,
iron .
Atoms iron In In
of reactants
products
1) Initial 9 ( in Fe) 3 Cin Fez Oa )
ii) To balance 9×3 3
3. Fe t 4h20 →
Fez Oat 4th
Writing Symbols of Physical State :
To make chemical informative the
equation physical States of the reactan
•
a more ,
and products with their
are mentioned
along chemical
formulae .
reactants
gaseous liquid aqueous and
The solid States
of and
products are
•
, ,
represented by the notations ( g ) Cl) , ,
Cs) and Cag) respectively .
