A chemical equation is an expression that gives the identities and quantities of the substances in a chemical reaction Chemical formulas and other symbols are used to indicate the starting material(s) or reactant(s), which are written on the left side of the equation, and the final compound(s) or product(s), which are written on the right side. An arrow, read as yields or reacts to form, points from the reactants to the products. Abbreviations are added in parentheses as subscripts to indicate the physical state of each species:—( s ) for solid, ( l ) for liquid, ( g ) for gas, and ( aq ) for an aqueous solution. A balanced chemical equation is when both the numbers of each type of atom and the total charge are the same on both sides. A chemical reaction represents a change in the distribution of atoms but not in the number of atoms. http://img.alibaba.com/photo/10784694/Aluminum_Oxide_Abrasive_Fine_Grit_120_220_.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Corundum_Aluminum_Oxide_Gallantin_Co_MontanaDSC03201.jpg/600px-Corundum_Aluminum_Oxide_Gallantin_Co_MontanaDSC03201.jpg http://www.germes-online.com/direct/dbimage/50327532/Aluminum_Alloy_Pipe.jpg
Objectives: To identify seven elements that occur naturally as diatomic molecules, H 2 , N 2 , O 2 , F 2 , Cl 2 , Br 2 , I 2 . [HOBrFINCL twins or BrINClHOF brothers] To write a chemical equation from the description of a chemical reaction.
Chemical equation & writing equation
By : AdityaKumar Pathak
• Chemical Equation (i)
• Chemical Equation (ii)
• Characteristicsof Chemical Equations
• Chemical equation: Reactant, Product & Chemical equation.
• Typesof Chemical equation
• Word equations
• Writing word Equations(i)
• Writing word Equations(ii)
• Writing symbol Equations
• Unbalanced and Balanced Equations
• Balancing of Chemical Equation (i)
• Balancing of Chemical Equation (ii)
A Chemical equation linkstogether the
substanceswhich react (Reactants) with
thenew substancesthat areformed
H2 + O2 H2O
Depict the kind of reactantsreactants and productsproducts
and their relative amounts in a reaction.
4 Al(s) + 3 O2(g) 2 Al2O3(s)
The numbers in the front are called
stoichiometric coefficientsstoichiometric coefficients.
The letters (s), (g), and (l) are the
physical states of compounds.
• The equation must represent known
• The equation must contain the correct
formulas for the reactants and products.
• The law of conservation of mass must
• Reactants – the substances that exist before
a chemical change (or reaction) takes place.
• Products – the new substance(s) that are
formed during the chemical changes.
• CHEMICAL EQUATION indicates the reactants
and products of a reaction.
TheChemical equation areof two types.
• A WORD EQUATION describes chemical change using
the names of the reactants and products.
Write the word equation for the reaction of methane gas with oxygen gas to
form carbon dioxide and water.
methane + oxygen
O2 CO2 H2O+ + 22
carbon dioxide + water
A word equation linkstogether thenamesof
thereactantswith thoseof theproducts.
For example, theword equation when
magnesium ribbon burnsin oxygen to form
awhitepowder of magnesium oxide, may
Magnesium + Oxygen Magnesium Oxide
In aword equation :
Thereactantsarewritten on theleft hand
sidewith plussign (+) between them.
Theproductsarewritten on theright hand
sidewith plussign (+) between them.
An arrow ( ) separatesthereactants
Thedirection of thearrow head points
A brief representation of achemical reaction
in termsof thesubstancesinvolved.
In asymbol equation, thesymbol and
formulaeof theelementsand compounds
arewritten instead of their word names.
For example, burning of magnesium in
oxygen to form magnesium oxidemay be
Mg + O2 MgO INDE
H2 + Cl2 HCl H2 + Cl2 2 HCl
Balancing of chemical equation may be
Theprocessof making thenumber of
different elementson both slidesof the
Themajor stepsinvolved in balancing achemical equation
Writethechemical equation in theform of aword equation.
Keep thereactantson theleft sideand theproductson right
side. Separatethem by an arrow head ( ) pointing
Convert theword equation into thesymbol equation by
writing thesymbolsand formulaeof all thereactantsand
Maketheatomsof different elementson both sidesof the
equation equal by asuitablemethod. Thisisknown as
balancing of equation. INDE
I. Which of thefollowing isachemical equation
(i) Mg - O MgO (ii) H2
+ Cl2 HCl
(iii) 2H2 + O 2 2H2O
(iv) Mg + Cl MgO