TYPES OF CHEMICAL REACTION & ACID BASE REACTIONS
Types of Chemical ReactionCombustion:A combustion reaction is when oxygencombines with another compound toform water and carbon dioxide. Thesereactions are exothermic, meaning theyproduce heat. An example of this kind ofreaction is the burning of napthalene:C10H8 + 12 O2 ---> 10 CO2 + 4 H2O
2) Synthesis:A synthesis reaction is when two or moresimple compounds combine to form amore complicated one. These reactionscome in the general form of:A + B ---> ABOne example of a synthesis reaction is thecombination of iron and sulfur to form iron(II) sulfide:8 Fe + S8 ---> 8 FeS
3) Decomposition:A decomposition reaction is the opposite of asynthesis reaction - a complex molecule breaksdown to make simpler ones. These reactionscome in the general form:AB ---> A + BOne example of a decomposition reaction is theelectrolysis of water to make oxygen andhydrogen gas:2 H2O ---> 2 H2 + O2
4) Single displacement:This is when one element trades places withanother element in a compound. Thesereactions come in the general form of:A + BC ---> AC + BOne example of a single displacement reactionis when magnesium replaces hydrogen in waterto make magnesium hydroxide and hydrogengas:Mg + 2 H2O ---> Mg(OH)2 + H2
5) Double displacement:This is when the anions and cations of twodifferent molecules switch places, forming twoentirely different compounds. These reactionsare in the general form:AB + CD ---> AD + CBOne example of a double displacement reactionis the reaction of lead (II) nitrate with potassiumiodide to form lead (II) iodide and potassiumnitrate:Pb(NO3)2 + 2 KI ---> PbI2 + 2 KNO3
Svante Arrhenius“ An acid is substance when dissolved in water yield H +ve ion”. “A base is substance when dissolved in water yield OH -ve ion”.
Example:This leads to the definition that in Arrheniusacid–base reactions, a salt and water is formedfrom the reaction between an acid and a base.In other words, this is a neutralization reaction.acid+ + base− → salt + waterThe positive ion from a base forms a salt with thenegative ion from an acid. For example, twomoles of the base sodium hydroxide (NaOH) cancombine with one mole of sulfuric acid (H2SO4)to form two moles of water and one mole ofsodium sulfate.2 NaOH + H2SO4 → 2 H2O + Na2SO4
Brønsted–Lowry definitionThe Brønsted–Lowry definition, formulated in1923, independently byJohannes Nicolaus Brønsted in Denmark andMartin Lowry in England, is based upon the ideaof protonation of bases through thede-protonation of acids—that is, the ability ofacids to "donate" hydrogen ions (H+) or protonsto bases, which "accept" them.Unlike theprevious definitions, the Brønsted–Lowrydefinition does not refer to the formation of saltand solvent, but instead to the formation ofconjugate acids and conjugate bases, producedby the transfer of a proton from the acid to thebase.
Example:The removal of H+ from hydrochloric acid(HCl) produces the chloride ion (Cl−), theconjugate base of the acid:HCl → H+ + Cl−The addition of H+ to the hydroxide ion(OH−), a base, produces water (H2O), itsconjugate acid:H+ + OH− → H2O