What exactly is Titration?
Titration is frequently referred to as “Titrimetry.” It is a chemical method for determining the concentration of an unknown sample by comparing it to the concentration of a standard solution. Titration is a type of volumetric analysis involving measurements of volume.
A titration technique involves primarily a burette and a conical flask.
• The standard solution whose concentration is known is contained in a burette.
• An unidentified analyte or sample is contained in a conical flask.
Titrant (standard solution) is an additional reactant to the titrand (sample to be analyzed). Once the mole concentrations of the titrant and titand are equalized, the solution’s properties will alter.
Typically, an indicator detects a change in a solution through colour changes. Finally, the volume of titrant added to the titrand can be calculated.
Important Terms
• Titrant or Titrator is a recognized concentration and volume standard solution.
• Titrand is an unidentified analyte or sample with an undetermined concentration and volume. The solution against which a titrant reacts.
• The volume of titration is the volume of titrant that reacted with titrand.
• An indicator is an organic dye that changes the colour of a solution to determine the equivalence point.
• The equivalence point or stoichiometric point occurs when the amount of titrant added equals the amount of the analyte being measured.
• The endpoint occurs when the system’s colour changes, indicating that the titration is complete.
One of the titration procedures is acid-base titration. First and foremost, we must understand what titration is and what is required to reach a conclusion.
An acid-base titration is a quantitative analysis technique for estimating the concentration of an acid or base by neutralizing it with a known-concentration standard solution of base or acid.
What is the purpose of acid-base titration?
An acid-base titration is an experimental method used to get information about a solution containing an acid or a base.
Through acid-base reactions, acid-base titrations are typically used to determine the concentration of a known acidic or basic chemical. The unknown molarity solution is the analyte (titrand). The reagent (titrant) is the known molarity solution that will react with the analyte.
Hundreds of chemical and inorganic substances can be identified by titration using their acidic or basic characteristics. The base is titrated with acid and acid is titrated with a base. Typically, the endpoint is discovered by adding an indication.
Informational Objective
Determining the concentration of an acid or base by measuring the volume of a titrant (of known concentration) that reacts with it in a stoichiometric proton-transfer reaction.
Theory
In an acid-base titration, strong or weak acids or bases are utilized. In particular, an acid-base titration can be utilized to determine the following:
1. The strength of an acid or base
2. How powerful or weak an unknown acid or base is.
3. the pKa or pKb of the unknown acid or base.
Consider an acid-base reaction that is occurring in the presence of a proton acceptor. Typically, the proton is solvated in water as H3O+. Adding H2O to the base causes it to lose (OH–) or gain (H3O+). Reversible acid-base reactions can occur.
The responses are displayed below.
HA + H2O → H3O+ + A– (acid)
B– + H2O → BH + OH– (base)
Here [A–] represents the conjugate base, whereas B-H represents the conjugate acid. Thus we assert
Acid + Base ⇋ Conjugate base + Conjugate acid
Types of Acid-Base Titration
The following table lists the types and examples of strong/weak acids and bases.
| S.No | Types | Examples |
| 1. | Strong acid-strong base | Hydrochloric acid and sodium hydroxide |
| 2. | Weak acid-strong base | Ethanoic acid and sodium hydroxide |
| 3. | Strong acid-weak base | Hydrochloric acid and ammonia |
| 4. | Weak acid-weak base | Ethanoic and ammonia |
Titration Curve & Equivalence Point
In titration, the equivalence point is the point at which the exact same number of moles of hydroxide ions and hydrogen ions have been added. If the base is added from the burette and the acid has been correctly metered into the flask, the titration is complete. The shape of each titration curve is characteristic of the particular type of acid-base titration.
The pH does not fluctuate in a consistent manner as acid is introduced. Each curve features horizontal regions where plenty of bases can be added without significantly altering the pH. There is also a part of each curve that is quite steep, with the exception of the weak acid and weak base curves, where a single drop of the base can alter the pH by many units. Even though the pH change at the equivalence point is not centered on pH 7, it is significant. This pertains to the selection of indicators for each titration type.
Choice of Indicators
Acid-base indicators are chemicals that alter colour or become cloudy at a specific pH. They determine the equivalency point and measure pH. They are themselves acids or bases, and they are soluble, stable, and undergo dramatic colour changes. They are natural in origin.
The colour change is caused by a resonance of electron isomerism. Diverse indicators have distinct ionization constants, and as a result, their colour changes at distinct pH intervals.
Acid-base indicators can be roughly categorized into three distinct categories.
- The phthaleins and sulphophthaleins (eg; Phenolphthalein)
- Azo indicators (eg; Methyl orange)
- Triphenylmethane indicators (eg; Malachite green)
Phenolphthalein and methyl orange are two typical indicators used in the acid-base titration. In each of the four types of acid-base titration, the base is introduced to the acid. The relationship between pH and the amount of base added is depicted in the graph below. Over what pH range do the two indicators change colour? Within the vertical region of the pH curve, the indicator must shift.
Acid-base indicators can be roughly categorized into three distinct categories.
The Choice of indicators based on the type of titration is tabulated below.
| Types of titration | Indicators |
| Strong acid-strong base | Phenolphthalein is usually preferred because of its more easily seen colour change. |
| Weak acid-strong base | Phenolphthalein is used and changes sharply at the equivalence point and would be a good choice. |
| Strong acid-weak base | Methyl orange will change sharply at the equivalence point. |
| Weak acid-weak base | Neither phenolphthalein nor methyl orange is suitable. No indicator is suitable because it requires a vertical portion of the curve over two pH units. |
Frequently Asked Questions – FAQs
Why is acid base titration important?
The goal of a strong acid-strong base titration is to determine the concentration of an acid solution by titrating it with a known concentration of a basic solution, or vice versa until neutralization occurs. The consequence of the reaction between a strong acid base and a strong base will be water and salt.
What are the applications of acid-base titration?
An acid-base titration is used to estimate the concentration of an unknown acid or base by neutralizing it with a known concentration of acid or base. Using the reaction’s stoichiometry, the unknown concentration can be estimated.
Which indicator is used in acid-base titration?
Using a phenolphthalein indicator, a titration between a strong acid and a strong base is done. Phenolphthalein is chosen because of its pH-dependent color change between 8.3 and 10. It will look pink in basic solutions and clear in acidic ones.
What are two acid-base indicators?
The acid-base indicators red cabbage juice, litmus paper, and phenolphthalein are examples. A weak acid or weak base that dissociates in water to form the weak acid and its conjugate base, or the weak base and its conjugate acid, is an acid-base indicator. The conjugation and species are of various colors.
Define the Equivalence point.
The point at which just enough reagent is added for a substance to react entirely.
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