Acid–base titration is a method to determine the concentration of an unknown acid or base by neutralizing it with a solution of known concentration. The process involves using indicators to identify the endpoint of the reaction, with different indicators suited for various acid-base combinations. Titration curves help visualize the data, and the process is vital in quantitative chemical analysis.

1. ACID BASE TITRATION
MD. Toufiq Hasan Anik
Date :05.07.215

2. Acid–base titration
An acid–base titration is the process which determines the concentration of an acid or base
.Which exactly neutralize the acid or base with an acid or base of known concentration.
Through acid base reactions Acid-Base titrations usually find the amount of a known acidic or
basic substance. This enables the quantitative analysis of the concentration of an unknown acid
or base solution. It work with following the neutralization reaction that occurs between acids
and bases. To find percent purity of chemicals Acid–base titrations can also be used.
By dissolving the substance being studied into a solution the analyte is prepared. The solution
is generally placed in a flask for titration. Then With the analyte a small amount of indicator is
added into the flask. The reagent is normally kept in a burette and slowly added to the analyte
and indicator mixture. The amount of reagent used is recorded when the indicator cuses a
change in the colour of the solution.
From Henderson-Hasselbalch equation: pH + pOH = 14
pH = pKa+log{[base]/[acid]}
A useful indicator has a strong color that changes quickly near its pKa. The indicator should
also have a pKa value near the pH of the titration's endpoint.
The pH of the equivalence point can be estimated using the following rules:
 A strong acid will react with a strong base to form a neutral (pH = 7) solution.
 A strong acid will react with a weak base to form an acidic (pH < 7) solution.
 A weak acid will react with a strong base to form a basic (pH > 7) solution.
Acid–base titration is performed with a bromthymol blue indicator, when it is a strong acid –
strong base titration, a phenolphthalein indicator in weak acid – strong base reactions, and a
methyl orange indicator for strong acid – weak base reactions. If the base is off the scale, i.e. a

3. pH of >13.5, and the acid has a pH >5.5, then an Alizarine yellow indicator may be used. On
the other hand, if the acid is off the scale, i.e. a pH of <0.5, and the base has a pH <8.5, then a
Thymol Blue indicator may be used.
A titration curve is drawn by plotting data attained during a titration, titrant volume on the x-
axis and pH on the y-axis. The titration curve serves to profile the unknown solution. The
titration of a strong acid with a strong base produces the following titration curve:
The equivalence point for a strong acid-strong base titration curve is exactly 7 because the salt
produced does not undergo any hydrolysis reactions. At equivalence point pH + pOH = 14.
For example ,an unknown molarity of HCl acts as the analyte. 50 mL of it is placed into a flask
and a 0.1 M solution of NaOH will be the reagent. The endpoint is pH=7 so litmus, with a pKa
of 6.5 is chosen. The color of the solution changes when 10 mL of 0.1 M NaOH is added.The
balanced neutralization reaction:
HCl(aq)+NaOH(aq)→H2O(l)+Na++Cl−
Or just the net ionic equation
H++OH−→H2O(l)
The following equation can then be derived
X=0.0010molofHCl
The molarity is now easily solved for
0.0010molHCl0.050L=0.020MHCl
Finally, acid base titration is the process is widely used, important and easy chemical process
to determine concentration of acid and base which play an important role in chemical industry.