Showing posts with label Volumetric titration. Show all posts
Showing posts with label Volumetric titration. Show all posts

Wednesday, August 10, 2022

What solution usually goes in the burette in titration?

The titrant is a known concentration solution that is placed in the burette, and the analyte is a solution of unknown concentration that is poured into a conical flask. In an acid-base titration, the base, such as sodium hydroxide (NaOH), is often taken in a burette, whereas the acid, such as hydrochloric acid (HCl), is typically taken in a conical flask.

Titration, also known as titrimetry, is a type of quantitative analysis used to determine the concentration of a substance. To determine the endpoint an indicator is used that changes the color of the solution after the endpoint or equivalence point is reached. Based on chemical reactions, there are four types of titrations: acid-base, redox, precipitation, and complexometric titrations.

Which solution is in burette in titration?

When performing titrations, the solution is often placed in a burette, known as a titrant. In analytical chemistry, the titrant is a solution with a known concentration that is added to another solution to measure the concentration of analytes.

The known (concentration) solution is taken in a conical flask, and the solution whose concentration or strength you are trying to determine, i.e., titrant, is taken in a burette.

Titration is performed between two interacting solutions. The purpose is to determine the precise volume of a solution that reacts with a known concentration of other solutions.

Typically, a pipette that can only measure a single fixed volume, such as 10 ml or 20 ml, is used to take the known volume. A small amount of the other solution is taken into the burette and added dropwise into the solution, which is taken in a conical flask. That's why we use a burette in the titration.



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Tuesday, August 9, 2022

Sources of error in titration

Titration also known as volumetric analysis or titrimetry is a method of determining the concentration of an unknown solution. It is a quantitative technique in which a reaction between the titrant and titrand takes place. The titrant is the substance whose concentration is known, and the titrand or analyte is the compound to be tested.

The endpoint of the reaction is detected using an indicator; this indicator changes the color of the solution. In chemistry, different types of titrations, such as acid-base, precipitation complexometric, and redox titrations, are used for various purposes and pharmaceutical research.

Titration is a highly sensitive analytical technique that allows us to determine the concentration of an unknown sample in solution by introducing a compound with a known concentration. Therefore, it must be carried out precisely to get the desired results.

Possible sources of errors in titration:

There are two different kinds of titration errors: random errors and systematic errors. Errors in titration can be caused by several different things, including human error and some of the other things that are listed below.
  • Misinterpretation of colors
  • End Point Error
  • Misreading the volume
  • Use of contaminated solutions
  • Using solutions with the incorrect concentration
  • Using the wrong amount of indicator
  • Improper use of equipment
  • Use of contaminated glassware
  • Inaccurate weight of material (Balance/weighing error)
  • Using the wrong solution to rinse the pipette and/or burette
  • Incorrectly filling the burette with liquid
  • Not transferring all solids or liquids while preparing samples
  • Transferring excess or less volume of liquid
  • Use of wrong chemicals or reagents
  • Performing the titration at the wrong temperature
  • Leakage in Burette
  • Use of the wrong procedure
  • The accuracy of volumetric glassware
  • Use of the same glassware for two different substances


Frequently Asked Questions (FAQ):

What do you mean by percentage error?

A percentage error represents the difference between the estimated value and the actual value, represented as a percentage. In other words, the percent error is the relative error multiplied by 100.

What is a titration error?

An error in titration is the difference between a titration's endpoint and an equivalence point. The volume of the endpoint that is higher or lower than the equivalence point is referred to as the titration error. The endpoint of the titration is the color change observed at the end of the reaction.



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Saturday, August 6, 2022

Volumetric Analysis: Principle, Types, Procedure & Applications

Learn about the principle, types, procedures, and applications of the volumetric technique which is used to determine the concentration of a substance using the known volume of a known substance.

Chemical analysis is an important part of the study of different materials or substances. It is broadly classified into two forms: qualitative analysis and quantitative analysis. Qualitative chemical analysis is a branch of chemistry that that deals with the identification of elements or grouping of elements present in a sample.

Quantitative analysis is any technique used to determine the concentration of a substance in a sample. It is further divided into gravimetric analysis and volumetric analysis.

Titration, also called titrimetry, is a type of quantitative analysis that is used to determine the amount of a specific substance in an unknown given sample. Since measuring volume is the most important part of this analysis, it is also called volumetric analysis.

In the process, the titrant is added to the analyte until a certain endpoint or equivalence point is reached. The reaction's endpoint is identified using an indicator. The indicator causes the color of the solution when the endpoint is reached.


Definition of volumetric analysis:

"The process of titrating a solution to find out how much of a substance is in it, by volume"

What is volumetric analysis?

Volumetric analysis, also known as titration, is a quantitative chemical analysis technique that is used in laboratories to determine the concentration of an analyte by measuring the volume that it occupies or, more broadly, the volume of a second substance that combines with the first in known proportions, also known as titrimetric analysis.

In other words, volumetric analysis or titration refers to the process of measuring the volume of a second substance that combines with the first in known proportions. It is used in laboratories which allows us to determine the concentration of analyte. 

The titrant is a reagent that produced a standard solution with a specific volume and concentration. The titrant reacts with an analyte solution to determine the concentration of the analyte.

History of volumetric analysis:

The French chemist Jean-Baptiste-Andre Dumas derived and found the first volumetric analysis method while attempting to quantify the proportion of nitrogen with other elements in organic compounds.

To assure the conversion of the chemical into pure gas, the nitrogen compound was burned in a furnace and passed through the furnace in a stream of carbon dioxide (CO2) that is passed into a strong alkali solution. The mass of the nitrogen is calculated, which occupies the sample under conditions of pressure and volume that are already known.

Example of volumetric analysis:

Volumetric analysis refers to any method of quantitative analysis in which the quantity of a substance is determined by measuring the volume that it occupies the volume of a second substance that combines with the first substance in known proportions.

For example, acid-base titration, preparation, and standardization of sodium hydroxide (NaOH) solution.

Principle of volumetric analysis:

The following are some of the fundamentals of volumetric analysis:
  • The solution that needs to be examined must have an unknown number of chemicals.
  • To show the end-point of the reaction a chemical with an unknown amount reacts with a substance of unknown concentration in the presence of an indicator (E.g. phenolphthalein/methyl orange). The endpoint is the point at which a chemical process is complete.
  • The titration procedure, which measures the volumes, is used to complete the reaction between the titrant and titrand.
  • The amount of reagent and solution is represented by the volume and concentration of the reagent used in the titration.
  • The mole fraction of the equation determines the quantity of an unknown substance in a given volume of solution.
When the reaction reaches its endpoint, the volume of reactant consumed is measured and used to calculate the volumetric analysis of the analyte (molarity or normality) using the formula Ca= Ct Vt M / Va.

Types of volumetric analysis:

The volumetric analysis can be classified into the following three types:
  1. Simple titration
  2. Back titration
  3. Double titrations

1. Simple titration: 

A simple titration is a method of determining the concentration of an unknown solution using a solution of known concentration. The simple titration can be subdivided into the following four categories:

2. Back titration:

In a back titration, the concentration of an analyte is determined by reacting it with a known amount of excess reagent, whereas in a direct titration, the concentration of an unknown compound is examined directly. Back titration is also known as indirect titration in which excess reagents are not added.

3. Double titration:

These types of titrations are carried out to find out the percentage content of an acid or alkali mixture. Gilson's titration method is also known as double titration, which determines the concentration of organometallic compounds in hydrocarbon solvents.

In the first step, the base concentration in the solution is determined. The concentration of the metal-organic complex can be calculated in the second stage by determining the residual amount of alkali after the organometallic compound and halide react.

Procedure of volumetric analysis:

Common apparatus required to perform volumetric titration are burette, conical flask, beaker, pipette, funnel, volumetric flask, wash bottle, etc. Following are the steps used for volumetric analysis:
  1. All glassware should be cleaned and dried according to standard laboratory procedures.
  2. Remove air bubbles from the burette and adjust the reading to zero.
  3. By precisely weighing the chemicals, accurately prepare the standard solution and a sample of the material to be measured in the solution.
  4. A common titration begins with the placement of a conical flask underneath a burette, which contains the solution of analyte/sample and a few drops of suitable indicator (such as methyl orange or phenolphthalein).
  5. Then, the titrant is dropwise added to the analyte until a change in the indicator's color is observed, showing that the endpoint of the titration has been reached. This indicates that the amount of titrant present equals the amount of analyte present due to their interaction.
  6. Depending on the desired endpoint, a single drop of the titrant can cause either a temporary or permanent change in the color of the indicator.
  7. To get accurate results, repeat the titration three times, and properly record the readings of the burette. Take their mean and calculate the molarity/normality of the sample.
Volumetric Analysis: Principle, Types, Procedure & Applications

Applications of volumetric analysis:

Volumetric analysis is one of the fundamental analytical techniques in chemistry and is applied for quantitative analysis in life sciences, pharmaceuticals, clinical chemistry, cosmetic industry, water pollution, wastewater management, food industry, wine industry, etc.


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Tuesday, August 2, 2022

Why is titration known as volumetric analysis?

Titration, also known as volumetric analysis or titrimetry, is a method that is used to determine the concentration of an unknown solution. It is a quantitative method in which an reaction between the titrant and the titrand occurs. The titrant is the substance whose concentration is known, and the titrand (also known as analyte) is the compound that is analyzed.

An indicator is used to determine the endpoint of the reaction. When the endpoint has been reached, this indicator changes the color of the solution. However, sometimes the reactants themselves can act as an self indicator in which no indicator is needed.

There are different types of titration, including acid-base, redox, complexometric, and precipitation titrations, which are employed in chemistry and for pharmaceutical applications.

Why titration is also called volumetric analysis?

Due to the measurement of volume plays a key role in titration, it is also known as "volumetric analysis." It is a method of quantitative chemical analysis used in laboratories to detect the unknown concentration of an identified analyte.

Volumetric Analysis: Volumetric analysis is a practical method in which reactive volumes are used to analyze and calculate a range of unknown values.

Titrations: A titration is a technique used for determining the concentration of an unknown solution.



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Saturday, July 9, 2022

What is acid base titration in chemistry?

Titration is also known as titrimetry is a quantitative and volumetric method for determining the concentration of an unknown solution using the concentration of a known solution in the presence of an indicator.

To determine the concentration of an analyte in a solution, it is necessary to slowly add a volume of titrant (typically with a burette) until the color of the indicator changes to indicate a chemical reaction.

In quantitative chemical analysis, there are four types of titrations in terms of their purposes and methods, such as acid-base titration, redox titrations, precipitation titrations, and complexometric titrations.

What is acid-base titration?

As you know, there are a lot of different compounds, both organic and inorganic. With the help of titration, you can determine their acidic or basic properties.

An acid-base titration is a quantitative analysis technique for determining the concentration of an acid or base by neutralizing it with a standard solution of acid or base of known concentration (Molarity).

Acid-base titrations involve neutralizing acids and a base therefore is also known as neutralization titration. It depends on the analyte's chemical interaction with a standard reagent.

Three different theories have been proposed to characterize acids and bases Arrhenius theory, Bronsted-Lowry theory, and the Lewis theory of acids and bases.

What is the principle of acid-base titration?

The acid-base titration principle is based on the neutralizing reaction that occurs between acid and base.
ACID + BASE ⇒ SALT + WATER

Strong/ weak acids or bases are used in acid-base titrations. It is used to determine how much acid or base there is. It is also used to determine the strength of an unknown acid or base. It determines the pKa of an unknown acid or pKb of an unknown base. 

Not every reaction can be called a titration. Consequently, a reaction can be considered a titration under certain conditions. 

The conditions are listed below:
  • The reaction must quickly.
  • A stoichiometric reaction should take place.
  • The change in free energy during the reaction must be sufficiently large.
  • There should be a method to determine the completion of the result.

What is an example of acid-base titration?

One example of an acid-base titration is the standardization of a NaOH solution usingCH3COOH, where sodium hydroxide is used as the strong base and is added to the burette, and acetic acid is used as the weak acid and is added to the conical flask. Acetic acid dissociation rises when a strong base is introduced to a weak acid.

What is the classification of acid-base titration?

Acid-base titrations are classified into four categories such as strong acid and strong base, weak acid and a strong base, weak base and strong acid, and weak acid and weak base.

Strong acid-strong base titration:
Example: Titration of hydrochloric acid (HCl) which is a strong acid and sodium hydroxide (NaOH) which is a strong base.

Weak acid and a strong base titration:
Example: Titration of acetic acid (CH3COOH) which is a weak acid and sodium hydroxide (NaOH) which is a strong base.

Weak base and strong acid:
Example: Titration of ammonia (NH3) which is a weak base and hydrochloric acid (HCl) which is a strong acid.

Weak acid and weak base:
Example: Weak acid includes formic Acid (HCOOH), Acetic Acid (CH3OOH), etc, and the weak base includes Ammonium Hydroxide (NH4OH), Ammonia (NH3)

What are indicators in acid base titration?

Acid-base indicators are weak acid or weak base that changes color as the concentration of hydrogen (H+) or hydroxide (OH-) ions in an aqueous solution changes. However, unlike other acids, the acid and base form the indicator have unique colors.

Indicators are often used in applications that require pH changes, such as titrations, pH tests, and science presentations because the color of the indicator depends on the pH of the solution.

The pH range of an indicator, which is dependent on the acid strength of the indicator, is its most important characteristic. The range of pH values over which an indicator changes color from its acid form to its base form is known as the indicator's pH range.

It extends from the highest pH, where only the acid form is visible, to the lowest pH, where only the basic form is visible. The indicator is insensitive to pH changes outside its range because it does not change color at these pH values.

Phenolphthalein and methyl orange are the two most common indicators used in the acid-base titration. Litmus is probably the best-known pH indicator. Common acid-base indicators include methyl red, thymol blue, bromocresol green, phenol red, etc.

What is the equivalence point in an acid-base titration?

The equivalence point is the point in a titration where the amount of titrant added is just enough to make the analyte solution completely neutral. In an acid-base titration, the equivalence point, moles of base = moles of acid, and the solution only contains salt and water. The endpoint of a reaction is the moment at which the reaction is completed.

It is essential to remember that endpoints and equivalence points may not be the same. As the equivalence point is determined by the stoichiometry of the reaction, whereas the endpoint is just the change in color of the indicator. 

Usually, the endpoint can be determined only after the addition of a slight excess amount of the titrant. If the endpoint is different from the equivalence point, then it amounts to an error in the experiment.


Key terms used in acid-base titrations:

  • Burette
A graduated glass tube having a tap at one end is used for titration to administer known volumes of liquid.
  • Analyte
A substance whose quantity/concentration is to be determined.
  • Titrant
A solution with a known concentration is filled in the burette that is added to another solution to find out the concentration of a second chemical species.
  • Buffer
A solution consisting of an acid and its conjugate base is used to control the pH of a solution.
  • pH
A measure of the hydrogen ion concentration is equal to - log [H+].
  • pKa
The pKa value describes the acidity of a certain molecule. The strength of an acid is determined by how tightly a proton is retained by a Bronsted acid.


Frequently Asked Questions (FAQ):


What is the titration curve in chemistry?

The plot of the pH of the analyte solution vs the volume of titrant applied added as the titration progresses.

Why is acid-base titration important?

The main purpose of a strong acid-strong base titration is to determine the concentration of an acid solution by titrating it with a solution of known concentration, or vice versa until neutralization occurs. Therefore, the reaction between a strong acid base and a strong base will produce water and salt.

What are the steps of acid-base titration?

The steps of acid-base titration are: selection of titrant and the titrate, selection of normality of titrate, select the amount of liquid you wish to pipette, selection of indicator, note the endpoint when solution changes color, and calculate the normality of the titrant using the final reading.

Which indicator is used in acid-base titration?

Common acid-base indicators include methyl red, thymol blue, bromocresol green, phenol red, etc. Phenolphthalein and methyl orange are the two most common indicators used in the acid-base titration. 

Litmus is probably the best-known pH indicator. Phenolphthalein is chosen because of its pH-dependent color change between 8.3 and 10. It shows pink in basic solutions and colorless in acidic ones.

Why is NaOH used in titration?

In a titration, sodium hydroxide is used if the unknown sample solution is acidic, as bases are utilized to neutralize acids.


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References:
  • Wikipedia contributors. "Acid–base titration." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 7 May. 2022.
  • GH Jeffery, J Bassett, J Mendham, RD Denney, Vogel's Textbook of Quantitative Chemical Analysis, 5th ed, 1989, Wiley, NY.


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Friday, April 29, 2022

Preparation and standardization of 0.1 M potassium iodate

Learn about the preparation and standardization of 0.1 M potassium iodate solution through a laboratory experiment or practical.

Aim:

To prepare and standardize 0.1 M potassium iodate solution using 0.1 M solution of sodium thiosulphate.

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, wash bottle, etc.

Chemicals: AR grade potassium iodate (KIO3), potassium iodide (KI), sulphuric acid (H2SO4), sodium thiosulphate (Na2S2O3), starch, etc.

Apparatus: Digital/analytical balance, and Ultrasonicator.

Preparation of starch solution:

Click here to get the procedure.

Preparation of 0.1M potassium iodate solution:

Take 21.4 gm of previously dried potassium iodate in 500 ml of water. Once it has completely dissolved, make up the volume to 1000 ml.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take 25.00 ml of prepared solution of potassium iodate into 200 ml of water. In 20.00 ml of this solution, add 02.00 g of potassium iodide and 10.00 ml of 1M sulfuric acid.
  • Add 01.00 ml of the starch indicator.
  • Titrate the sample solution with 0.1M sodium thiosulphate until the endpoint is reached. The actual endpoint indicates by colorless to blue starch-iodine complex.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.
  • Take their mean and calculate the molarity of ferrous ammonium sulphate.
  • 01 ml of 0.1M sodium thiosulphate is equivalent to 0.003566 gm of KIO3.

Observation table:

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Preparation and standardization of 0.1 M ferrous ammonium sulphate

Learn about the preparation and standardization of 0.1 M ferrous ammonium sulfate solution through a laboratory experiment or practical.

Aim:

To prepare and standardize 0.1 M ferrous ammonium sulphate solution using 0.1 M solution of ceric ammonium sulphate.

Requirements:

Glasswares: 
Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, wash bottle, etc.

Chemicals:
LR grade ferrous ammonium sulphate (FeH8N2O8S2), ceric ammonium sulphate ((NH4)4Ce (SO4)4), ortho-Phenanthroline (C36H24FeN6+2), sulphuric acid (H2SO4), etc.

Apparatus: 
Digital/analytical balance, and Ultrasonicator.

Preparation of 0.1 M ferrous ammonium sulphate solution:

Take 160 ml of distilled water, add 40 ml of sulphuric acid, and once it is cooled then weigh 40 gm of ferrous ammonium sulphate and add it. Once it has completely dissolved, make up the volume to 1000 ml.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take 25.00 ml of prepared solution of ferrous ammonium sulphate and pour it into a conical flask.
  • Add 2 drops of ortho-Phenanthroline indicator.
  • Titrate the sample solution with 0.1M ceric ammonium sulfate until the endpoint is reached. The actual endpoint of the reaction is red color changes to a blue one.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.
  • Take their mean and calculate the molarity of ferrous ammonium sulphate.
  • 01 ml of ceric ammonium sulphate is equivalent to 0.03921 gm of Fe (NH4)2(SO4)2,6H2O.

Observation table:
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Friday, April 15, 2022

Why do we need to standardize NaOH solution?

In chemistry, the process of determining the precise concentration (molarity) of a solution is known as standardization. One of the most important preconditions for reliable and transparent titration determination is the so-called titer standardization/determination of the volumetric solution used for the titration.

In the titration procedure, the titrant is usually added to a known quantity of analyte (the unknown solution) from a burette until the reaction is complete. The concentration of the unknown can be determined by knowing the volume of titrant added. An indicator is often used to indicate the endpoint, or equivalence point, of the reaction.

Why is there a need to standardize the NaOH solution?

To find out the exact concentration (molarity/normality) of the prepared NaOH solution, it needs to be standardized. Unfortunately, sodium hydroxide is not a good primary standard. Since solid NaOH is highly hygroscopic, it cannot be weighed precisely. It absorbs carbon dioxide (CO2) from the air, forming sodium carbonate and lowering the amount of NaOH. 

So we'll need to determine the exact concentration of the prepared NaOH solution that has the approximate concentration. The concentration of NaOH can be determined precisely by titrating a potassium hydrogen phthalate (KHP) sample of known mass with the prepared NaOH solution.

What does it mean to standardize a NaOH solution?

Standardization is the process of finding the exact concentration (molarity) of a solution. The molarity of a sodium hydroxide solution will be measured in the first standardization by titrating a sample of KHP with the NaOH.

Why is the standardization of NaOH necessary?

Because sodium hydroxide is hygroscopic, it absorbs moisture from the air quickly, changing its concentration.

Why standardized NaOH should be kept in a stoppered bottle?

As atmospheric carbon dioxide reacts with the stored NaOH to form carbonic acid when it comes into contact with it. As a result, the concentration of the base decreases. Therefore, sodium hydroxide must be kept in a closed bottle to avoid interaction with atmospheric carbon dioxide.
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