Points to Remember

Types of Chemical Reactions

Points to Remember

·                 A chemical change is a change in which one or more new substances are formed.

·                 Aerobic: Presence of oxygen.

·                 Anaerobic: Absence of oxygen

·                 Most combination reactions are exothermic

·                 Electrolytic decomposition reaction may occur in the presence of heat or light.

·                 All photo decomposition reaction are endothermic reactions.

·                 Double displacement reaction or

·                 metathesis may occur by the mutal

·                 exchange of ions.

·                 Precipitation reaction gives an insoluble salt as the product.

·                 Neutralisation reactions are reactions between an acid and a base that forms salt and water.

·                 Plants can not grow in an acidic soil. Neutralisation prevents tooth decay.

·                 Most reactions in chemistry are irreversible reactions.

·                 Chemical equilibrium-the rate of the forward reaction is equal to rate of the back ward reactions.

·                 Equilibrium is possible in a closed system. Temperature increases the reaction rate. Pressure increases the reaction rate.

·                 The term pH means power of hydrogen. pH plays a vital role in everyday life.

·                 In humans all bio chemical reactions take place between the pH value of 7.0 to 7.8.

·                 If pH of rain water is below 5.6 its called acid rain.

·                 Pure water is a weak electrolyte.