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Lorenz Delocado. Sourav Paul. Vamsi Bonagiri. Show More. No Downloads. Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. This allows for quantitative analysis of the concentrationof an unknown acid or base solution. It makes use of the neutralizationreaction that occurs between acids and bases.
Acid—base titrations can also be used to find percent purity of chemicals. Alkalimetryand Acidimetry Alkalimetry and acidimetry are a kind of volumetric analysis in which the fundamental reaction is a neutralization reaction. Alkalimetry is the specialized analytic use of acid-base titration to determine the concentrationof a basic synonymous to alkaline substance.
Acidimetry, sometimes spelled acidometry, is the same concept of specialized analytic acid-base titration, but for an acidic substance.
Method Before starting the titration a suitable pH indicator must be chosen. The equivalence point of the reaction, the point at which equivalent amounts of the reactants have reacted, will have a pH dependenton the relative strengths of the acid and base used.
When a weak acid reacts with a weak base, the equivalence point solution will be basic if the base is stronger and acidic if the acid is stronger. If both are of equal strength, then the equivalence pH will be neutral. However, weak acids are not often titrated against weak bases because the colourchange shown with the indicator is often quick, and therefore very difficult for the observer to see the change of colour.
The point at which the indicatorchanges colouris called the end point. A suitableindicator should be chosen, 4. First, the buretteshouldbe rinsed with the standard solution, the pipettewith the unknown solution, and the conical flask with distilled water. Secondly, a known volume of the unknown concentration solution should be taken with the pipetteand placed into the conical flask, along with a small amount of the indicatorchosen.
The known solution should then be allowed out of the burette, into the conical flask. At this stage we want a rough estimate of the amount of this solution it took to neutralizethe unknown solution. The solution shouldbe let out of the buretteuntil the indicatorchanges colour and the value on the buretteshouldbe recorded. This is the first or rough titration volume and should be excluded from any calculation. At least three more titrations should be performed, this time more accurately, taking into account roughly where the end point will occur.
The initial and final readings on the burette prior to starting the titration and at the end point, respectively should be recorded. Subtractingthe initial volume from the final volume will yield the amount of titrant used to reach the end point. The end point is 5. Acid—base titration is performed with a bromthymol blue indicator, when it is a strong acid — strong base titration, a phenolphthalein indicatorin weak acid — strong base reactions, and a methyl orange indicator for strong acid — weak base reactions.
If the base is off the scale, i. On the other hand, if the acid is off the scale, i. Titrationof weak acid The pH of a weak acid solution being titrated with a strong base solution can be found at different points along the way. These points fall into one of four categories: 6. The initial pH is approximated for a weak acid solution in water using the equation where Ka is the dissociation constant and F is the concentrationof the acid.
The pH before the equivalencepoint dependson the amount of weak acid remaining and the amount of conjugate base formed.
When the numeratorof the log term equals the denominator , then the ratio goes to 1 and the log term goes to zero. Thus the pH will equal the pKa which occurs half-way to the equivalence point. Animation of titration with base titrant 3. At the equivalencepoint, the weak acid is consumed and converted to its conjugate base. The pH will be greater than 7 and can be calculatedfrom an equation derived from the following relationships: 1. The pH dependson the strengths of the acid and base. After the equivalencepoint, the solution will contain two bases: the conjugate base of the acid and the strong base of the titrant.
However, the base of the titrant is stronger than the conjugate base of the acid. Therefore, the pH in this region is controlled by the strong base.
As such the pH can be found using the following: Single formula. More accurately, a single formula that describes the titration of a weak acid with a strong base from start to finish is given below: 9. You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips. Visibility Others can see my Clipboard. Cancel Save.
An acid—base titration is a method of quantitative analysis for determining the concentration of an acid or base by exactly neutralizing it with a standard solution of base or acid having known concentration. A pH indicator is used to monitor the progress of the acid—base reaction. If the acid dissociation constant p K a of the acid or base dissociation constant P K b of base in the analyte solution is known, its solution concentration molarity can be determined. Alternately, the p K a can be determined if the analyte solution has a known solution concentration by constructing a titration curve. Alkalimetry and acidimetry are a kind of volumetric analysis in which the fundamental reaction is a neutralization reaction. Alkalimetry is the specialized analytic use of acid-base titration to determine the concentration of a basic synonymous to alkaline substance.