Chemical

Reactions

Chemical ReactionChemical reaction, a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

Chemical reactions happen at a characteristic reaction rate at a given

temperature and chemical concentration. Typically, reaction

rates increase with increasing temperature because there is more

thermal energy available to reach the activation energy necessary for breaking bonds between atoms.

  

The substance (or substances) initially involved in a chemical reaction are called reactants or reagents.

Chemical reactions are usually characterized by a chemical change, and they yield one or more products,

which usually have properties different from the reactants. Reactions often consist of a sequence of

individual sub-steps, the so-called elementary reactions, and the information on the precise course of

action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which

symbolically present the starting materials, end products, and sometimes intermediate products and

reaction conditions.

Indicators of Chemical Reaction

Evolution

Of heat

Evolution of gas

Change in color

Formation of odor

Formation of

precipitate

Types Of Chemical Reactions

The general form of a synthesis reaction is A + B → AB. Synthesis reactions "put things together".This reaction releases a tremendous amount of heat and light energy. This is the most well-known example of a synthesis reaction—the formation of water via the fusion of hydrogen gas and oxygen gas.

EXAMPLES:Na (s) + Cl2 (g) → NaCl (s) Ca (s) +O2 (g) → CaO (s) SO3 (s) + H2O (l) → H2SO4 (s)

Synthesis Reactions

Dec

ompo

siti

on

Reac

tion

s These are the opposite of synthesis reactions, with the format AB → A + B. Decomposition reactions "take things apart". Just as synthesis reactions can only form one product, decomposition reactions can only start with one reactant. Compounds that are unstable will decompose quickly without outside assistance.One example is the electrolysis of water (passing water through electrical current) to form hydrogen gas and oxygen gas.

EXAMPLES:H2O H2(g) + O2(g)

HgO Hg(s) + O2(g)

y electricit

Single Replacement Reactions

Single replacement reactions, also called single displacement, swap one component with another, in the format AB + C → AC + B.EXAMPLE:2Na + SrCl2 Sr + 2NaClF2 + LiCl LiF + Cl2

Dou

ble

Repl

acem

ent

Reac

tion

s

Two things replace each other.Reactants must be two ionic compounds or

acids.Usually in aqueous solution

AB + CD AD + CB

EXAPLES : ZnS + 2HCl ZnCl + H2S

AgNO3 + NaCl AgCl + NaNO3

CombustionCombustion, better known as burning, is the combination of a substance with oxygen. The products are carbon dioxide, water, and possible other waste products. Combustion reactions release large amounts of heat. Combustion is similar to a decomposition reaction, except that oxygen and heat are required for it to occur. EXAMPLE:CH4 + O2 CO2 + H2OC3H8 + O2 CO2 + H2O

Acid/Base Reaction

In simple terms, an acid is a substance which can lose a H+ ion (i.e. a proton) and a base is a substance which can accept a proton. When equal amounts of an acid and base react, they neutralize each other, forming species which aren't as acidic or basic.Always in aqueous solutionAcid (H+) + Base (OH-) → Salt + H2OEXAMPLE:NaOH + HCl → NaCl + H2ONH4OH + H2SO4 → (NH4)2SO4 + H2O

Redox is an abbreviation of reduction/oxidation reactions. This is exactly what happens in a redox reaction, one species is reduced and another is oxidized. Reduction involves a gain of electrons and oxidation involves a loss, so a redox reaction is one in which electrons are transferred between species. Reactions where something is "burnt" (burning means being oxidized ) are examples of redox reactions, however, oxidation reactions also occur in solution, which is very useful and forms the basis of electrochemistry.

*Redox Reaction

The End

Made By,Shubham X – ‘ A ‘

Roll no. - 35