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What Is Titration? The Three Types of Titration Explained

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titration

What Is Titration?

Titration is defined as "a method or process of determining the concentration of a dissolved substance in terms of the smallest amount of reagent of known concentration required to bring about a given effect in reaction with a known volume of the test solution."

The Three Types of Titration

  1. Blank titration
  2. Back titration
  3. Direct titration

What Is an Indicator?

In chemistry, an indicator is defined as a substance that undergoes distinct observable change when the conditions of its solution change. Litmus is the most commonly used indicator in the laboratory.

What Is a Turning Point?

When an indicator is added in the solution and the color of the solution is changed, this is called the turning point.

Blank Titration

In a blank titration, we titrate the titrant (soln in burette) against the blank solvent in which a sample of unknown concentration (analyte) is dissolved. Now the end point where a notable color change is produced is found. This is done to ensure that either there are no substances in the solvent which can react with the titrant, or to estimate the amount of titrant that would react with the pure solvent. In this way, we can estimate the error that can be produced when the actual titration experiment is conducted.

Back Titration

A back titration is a titration method where the concentration of an analyte is determined by reacting it with a known amount of excess reagent. The remaining excess reagent is then titrated with another, second reagent. The second titration's result shows how much of the excess reagent was used in the first titration, thus allowing the original analyte's concentration to be calculated.

A back titration may also be called an indirect titration.

When Is a Back Titration Used?

A back titration is used when the molar concentration of an excess reactant is known, but the need exists to determine the strength or concentration of an analyte.

Back titration is typically applied in acid-base titrations:

  • When the acid or (more commonly) base is an insoluble salt (e.g., calcium carbonate)
  • When direct titration endpoint would be hard to discern (e.g., weak acid and weak base titration)
  • When the reaction occurs very slowly

Back titrations are applied, more generally, when the endpoint is easier to see than with a normal titration, which applies to some precipitation reactions.

How Is a Back Titration Performed?

Two steps are typically followed in a back titration:

  1. The volatile analyte is permitted to react with an excess reagent
  2. A titration is conducted on the remaining quantity of the known solution

A back titration is conducted when one of the solutions is highly volatile such as ammonia; a base or an acid is an insoluble salt such as calcium carbonate; a reaction is particularly slow or a direct titration entails a weak base and weak acid titration, the result of which is hard to ascertain.

A back titration is normally done using a two-step procedure. The analyte, which is the volatile substance, is first allowed to react with the excess reagent. A titration is then performed on the remaining amount of the known solution to determine how much is in excess and to measure the quantity consumed by the analyte.

Direct Titration

In a direct titration, a known excess of reagent that reacts with analyte is used. The excess is then measured with a second titrant.

What Is the Difference Between a Direct Titration and a Back Titration?

In a direct titration, a known excess of reagent that reacts with the analyte is used. The excess is then measured with a second titrant.

In a back titration, titrants react directly with the analyte.

In a direct titration, titrants react directly with the analyte.

In a back titration, a known excess of reagent that reacts with the analyte is used. The excess is then measured with a second titrant.

Comments

Sana mariam on June 02, 2020:

Titration is realy an enjoyable work during chemistry class

Obiora chinonso from Nigeria on June 02, 2020:

Back then titration was one of the practical aspect that I enjoined most in chemistery class ,things like observing a mixcture stating my prefence drawn a conclusion from my end products