Equivalence Poin.pptx...................

1. Equivalence Point References: 1-https://chemdictionary.org 2-https://byjus.com

2. Table Of Contents What is Equivalence Point Difference Between Equivalence point And End Point Methods of Determining The Equivalence Point I-pH indicator II-Conductance I II-Color Change IV-Precipitation V-Isothermal calorimetry VI-Amperometry VII-Spectroscopy VIII-Thermometric Titrimetry References

3. What is Equivalence Point? an equivalence point is a term that is used while performing titration. It applies to any acid-base or neutralization reaction technically. The equivalence point of a chemical reaction is the point at which equal quantities of reactants are mixed chemically.In other words, while titrating, it is a point where the amount of added titrant is enough to neutralize the analyte solution completely. The number of moles of titrant standard solution is equal to the moles of a solution having an unknown concentration. It is also known as the stoichiometric point because it is a point where the moles of acid is equal to the moles of the base that are needed to neutralize the solution. The equivalence point cannot be taken the same as the endpoint of a titration.The endpoint is referred to as the point at which the used indicator changes its color.These color changes appear after reaching the equivalence point. If we use the endpoint to determine equivalence, it will induce an error.

4. Difference Between Equivalence point And End Point Equivalence Point End Point A Point at which The titrant is Chemically Equivalent to the Analyte in the Sample Is a point Where The Indicator Changes Color Equivalence Point Can Vary In Weak Acid Weak Acids Have only one endpoint Occur Multiple In Times In a Reaction Especially In Polyprotic Acids With a Lot Of -OH ions Occurs once in a Reaction A Point at Which an Equivalent Or Stoichiometric amount of Titrant to The Analyte The point at which The Reaction Observed To Be Complete

5. Methods of Determining The Equivalence Point: I -pH indicator II -Conductance III -Color Change IV -Precipitation V -Isothermal calorimetry VI -Amperometry VII- Spectroscopy VIII -Thermometric Titrimetry

6. I -PH indicator A pH indicator is a chemical substance that changes its color in reaction to any chemical change. An acid-base indicator, for example, phenolphthalein changes its color which depends on its pH. Redox indicators can also be used for this purpose. The change in color will show that the endpoint has been attained. This will be an estimation of the equivalence point.

7. II- Conductance Conductometric methods measure the conductivity change between a pair of metal electrodes utilizing ion conductometric or impedimetric devices. The electrical conductivity of a solution is affected by the ions. Hence the conductivity changes when they react with each other. Conductance is relatively a difficult method to operate, especially when the ions that are present in the solution can participate in conductivity. Conductance can be used for a few acid-base reactions.

8. III -Color change At the equivalence point, the solution will change its color naturally without any addition of an indicator in some reactions. This may be observed in transition metals where the oxidation state consists of different colors.

9. IV -Precipitation During titration, the precipitate will form if the reaction forms a solid. A good example of precipitation is the reaction between silver, Ag+, and Chlorine, Cl- that results in the formation of an insoluble salt, Silver Chloride, AgCl. this makes it very hard to determine the endpoints accurately because of particle size, the rate of sedimentation and color makes it very difficult to see.This is the reason why precipitation titration is done as back titrations.

10. V -Isothermal Calorimetry one of the physical techniques that directly measures the heat discharged or consumed all along a bimolecular reaction The determination of the equivalence point is done by calculating the amount of heat that is produced or absorbed by using a device known as an isothermal titration calorimeter.This type is usually used in titrations that involve biochemical reactions.

11. VI -Amperometry Amperometry is a detection technique that is used to measure the change in the current. Amperometry is mostly used in those titrations where the excess titrant can be reduced. This method is helpful while titrating a halide with Ag+ because the formation of precipitates will not be affected.

12. VII -Spectroscopy spectroscopy is used to determine the equivalence point if the spectrum of the reactant, product or titrant is known. A specific amount of the product and reactant is used to find the equivalence point. A very low level of the free titrant’s presence can also be determined. In short, this method is used to determine the existence of semiconductors.

13. VIII -Thermometric Titrimetry The equivalence point is determined by measuring the rate of temperature change produced by a chemical reaction. This property differentiates it from calorimetric titrimetry. Because thermometric titrimetry is a relative technique, it is not necessary to perform the titration under isothermal conditions. To prevent stray draughts, these vessels are usually enclosed by causing any noise that disturbs the endpoint. Because of the ability of this type of titration to be conducted under ambient conditions.depending on whether the reaction taking place between the titrant and analyte is exothermic or endothermic. rate of temperature changes an increase or decrease determines the equivalence point and inflection in the temperature curve can be observed.