Chemical Reactions Summary

Symbol:

• It is a short hand notation of an element. E.g. sodium is denoted as Na.

Formula:

• It indicates the constituent elements and the number of atoms of each combining element. E.g. NaCl.

Chemical equation:

• It is a symbolic notation that uses formulae instead of words to represent a chemical equation.

Oxidation:

• The reaction in which a chemical species loses electron is called oxidation.

Reduction:

• The reaction in which a chemical species gains electron(s) is known as reduction.

Oxidising agent:

• The substance that oxidizes the other substance is called the oxidizing agent.

Reducing agent:

• The substance that reduces the other substance during a chemical reaction is called reducing agent.

Redox reaction:

• Reactions which can be explained on the basis of gain or loss of electrons is called redox reactions.

• In molecular compounds, the combining capacity i.e. the valency of each combining element determines the chemical formula of the compound.

• The valency of an electropositive ion and an electronegative ion is equal to the positive or negative charge on it.

• Reactants are substances that take part in a chemical reaction, while products are the new substances produced during the chemical reaction.

• When two or more elements or compounds react chemically to form one new compound, then the chemical reaction that takes place is a chemical combination reaction.

• When a chemical compound decomposes on heating or by some other way so as to form two or more compounds or elements then the reaction that takes place is called chemical decomposition.

• When a more active metal or nonmetal displaces a less active element from its aqueous salt solution, the reaction that takes place is called displacement or substitution reaction.

• A chemical reaction in which two ionic compounds in their aqueous solutions react by exchanging their ions/radicals to form to two new compounds is called chemical double decomposition.

• A polymerization reaction is one in which two or more molecules (monomers) combine to form a new bigger molecule.

• Chemical equations can be made more informative by indicating physical states, heat changes and condition under which the reaction takes place.

• A reaction in which heat is given out is exothermic. DH is negative

• A reaction in which heat is taken in is called endothermic. DH is positive.