Home CHEMISTRY TOPIC 5: VOLUMETRIC ANALYSIS | CHEMISTRY FORM 3

TOPIC 5: VOLUMETRIC ANALYSIS | CHEMISTRY FORM 3

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VOLUMETRIC ANALYSIS

VOLUMETRIC ANALYSIS

Standard Volumetric Apparatus

The Concept of Volumetric Analysis
Explain the concept of volumetric analysis
Volumetric analysis is a quantitative analysis involving the measurement of
different solutions. These solutions are made to react completely and the completion of the reaction is indicated by certain substances called indicators. The quantitative composition of the solution is then determined.

VOLUMETRIC ANALYSIS

Important steps of volumetric analysis include:

Weighing;Preparation of the solution;Titration; andCalculation

In volumetric analysis, we deal with volumes of solutions. That is why this quantitative determination of solutions of substances is called volumetric analysis.
The amount of a substance present in a solution is given in terms of its
volume and its concentration. The volume of a solution is usually given
in litres (dm3). The concentration of a solution is given in moles per litre (mol/dm3) or grams per litre (g/dm3).
Volumetric analysis is a means of finding the concentration of an unknown
solution. For example, the concentration of an unknown solution of an
acid can be found if it is reacted with a standard solution of an
alkali. A standard solution is one whose concentration is well known and does not change with time.

In volumetric analysis, the reaction is carried out in a carefully
controlled way. The volumes are measured accurately using a pipette and
burette. The method is to add a solution of one reactant to the solution
of another reactant until the reaction is complete.

When the reaction is complete, we say the end-point has been
reached. If the reactants are acids and bases, completion (end-point) is
determined by the change in colour of an acid-base indicator. The
method is called titration. In other reactions, completion is determined by a colour change of reactant(s).

The concentration of one of the reactant solutions must be known in
order to be able to find the concentration of unknown solution.

Significance of Volumetric Analysis

Volumetric
analysis is used to quantify the amount of substances present in
solutions by analytical procedure, which involves precise measurements
of volumes of solutions and masses of solids.Volumetric
analysis helps in the determination of the accurate volumes and
concentrations of the reacting substances, often solutions.Volumetric analysis (titration) helps in the preparations of standard solutions.Volumetric analysis knowledge helps in the standardization of acids and bases.

Volumetric Apparatus
Use volumetric apparatus
We
have seen that volumetric analysis involves determinations of
quantities of substances, usually acids and alkalis, present in volumes
of solutions. This is usually done by using measuring apparatus.
Apparatus
used in volumetric analysis is based on volume measurements and since
the analysis demands high accuracy, the apparatus has to be calibrated
with the highest possible accuracy. It is for this reason that all
apparatus for volumetric analysis are specifically for this and not
other purposes.
Apparatus
used for volumetric analysis include, burette, pipette, burette stand,
white tile, conical flask, filter funnel, reagent bottle, watch glass,
beaker, measuring cylinder and measuring flask (or volumetric flask).
For approximate measurements, measuring cylinders may be used. For
accurate measurements of volumes, volumetric flasks are used.
Burette

This
is a long glass tube with a narrow lower part, which is fitted with a
tap that controls the amount of solution let out of the burette. This
instrument is calibrated from 0 to 50 cm3.Before measuring
the solution, rinse the burette with distilled water, then with the
solution it is going to hold. It has to be filled to the tip and all gas
bubbles removed. Thus, the burette is an apparatus used for
transferring the solution to the titration vessel (normally a flask).

Burrete 1455104272831

Pipette

This
apparatus has a wider middle part with narrow parts at either ends. The
upper narrow part has a mark which marks the volume of all the space
below it. If, say, the pipette is one that is marked 25 cm3, we can say that a solution, when filled in the pipette up to this mark, will have a volume of 25 cm3.
VOLUMETRIC ANALYSIS

The
pipette is used in transferring a standard solution to the titration
flask. There are many types of pipettes depending on their volume
capacity. The common ones are the 25-cmand 20-cm3 capacity pipettes. Less common ones are the 10-cm3
capacity.Before measuring the solution, rinse the pipette several times
with distilled water and then with the solution to be measured; suck
the rinsing solution above the graduated mark, then discard the rinsing.

Pipete 1455104429028
The
pipette is commonly filled by mouth suction but the use of pipette
fillers is highly recommended. When using a pipette, never blow out the
last drop.
Pipetre 1455104578030

(a) A pipette (b) A pipette and pipette filler (used to fill and empty pipettes)
Measuring (Volumetric) flask

The
flask is made of glass and has a mark at the upper part of the narrow
tube. The space in the flask up to this mark represents a certain
volume. If a solution is filled up to this mark, the volume of the
solution is equal to the volume indicated by inscriptions on the flask
e.g. 50 cm3, 100 cm3, 150 cm3, 250 cm3, 500 cm3, etc.

Flask 1455104768407
Filter funnel
A
filter funnel is required for effective transfer of the weighed solid,
liquid or solution into the volumetric flask or burette.
Funnel 1455104939669

A filter funnel
Wash bottle
Wash
bottle contains water and when squeezed, water squarts out. This is
used in washing down the remains of the weighed solid into the
volumetric flask.
Bottle 1455105070657

A wash bottle

A weighing bottle
This is used in weighing the solute. It is a stoppered bottle. A watch glass can also be used to serve the same purpose.
VOLUMETRIC ANALYSIS
Retort stand

A burette stand is used for holding the burette in place while carrying out volumetric analysis experiments.

Standa 1455105254818

A burette stand
Dropper
A dropper is used to add the indicator dropwise into the solution.
Dropper 1455105464876
White tile or paper
A
white tile or piece of paper is placed under the flask to give a clear
background for accurate observation of the colour change at the end of
the reaction (end point).
Clay 1455105595612

VOLUMETRIC ANALYSIS

Application of Volumetric Analysis
The Application of Volumetric Analysis in Real Life Situations
Explain the application of volumetric analysis in real life situations
Volumetric
analysis has a variety of laboratory and industrial applications in
everyday life. The following are just a few of the applications (uses)
of volumetric analysis in daily life:

Use in preparation of standard solutions:Standard
solutions are prepared by applying the knowledge of volumetric
analysis. Volumetric analysis is used in school, college and university
chemistry laboratories to determine concentrations of unknown
substances. The titrant (the known solution) is added to a known
quantity of analyte (unknown solution) and a reaction takes place.
Knowing the volume of the titrant allows one to determine the
concentration of the unknown substance.

Use in environmental and water safety:Titration
is important in environmental chemistry, where scientists can use it to
analyze acid rain or contaminants in surface water samples.
Environmental studies usually involve an analysis of precipitation and
its response to pollution. To quantify the degree of contamination in
natural rainwater or snow, titration is used. The process is quick and
results are reliable. Since most titration processes do not require
expensive or specialized equipment, the test can be performed often and
in different areas with relatively little effort.The safety of water is
based on its chemical ingredients. By analyzing wastewater, the extent
of contamination and the requirements for filtering and cleaning can be
determined. Titration is a key mechanism in this analysis. Often, more
specialized titration equipment is used in this application, which
measures ammonia levels in combination with other reactants to quantify
other chemicals present.

Use in food and beverage industry:In
the food and beverage industry, manufacturers must ensure their
products meet certain quality criteria or contain standard
concentrations of specific additives, so titration is often used to
analyze the products before sale. Wine is often affected by its degree
of acidity. It is possible to improve wine production by measuring
acidity using titration. Simple, inexpensive titration kits are
available to winemakers for this purpose. The results of a titration
test on wine can suggest if additional ingredients are necessary to
maintain its quality.In general, all brewing industries and distilleries
apply the knowledge of volumetric analysis (titration) to determine the
acidity and alcohol contents of their beers and other alcoholic
beverages.The process also finds ample use in food industry. The
compounds which make up food products help determine their nutritional
implications. Titration is one technique that assists in these studies.
The acidity of orange juice, for example, is easily determined using a
standard titration process. In this process, an electrode is added to a
solution made up of orange juice and deionized water. The titrant
catalyst then measures the acidity of the juice. Manufacturers can use
the technique to vary this quality to satisfy customers or those with
special nutritional needs.

Use in agriculture:Volumetric
analysis technique is used to determine the soil pH. This is important
because, if the pH of a certain soil is found to be extremely low or
high, corrective measures are taken by adding the correct quantity of
agricultural limes or other chemicals to make the soil suitable for
plant growth.The method is also used by agronomists and farmers to
analyse the kind and amount of plant nutrient elements present in a
particular sample of soil, the knowledge of which helps determine soil
fertility.

Industrial and Laboratory Skills of Volumetric Analysis
Compare industrial and laboratory skills of volumetric analysis
The
knowledge of volumetric analysis (titration) is used in hospitals and
medical laboratories to carry out such duties as preparation of
solutions and suspensions, blood analysis, and diagnosis of certain
diseases and health problems. For example, when dissolving a solid drug
to make a solution for injection, utmost precision is required to
measure the correct volume of liquid to be used to dissolve a correct
amount of solid drug to prepare the solution of a given concentration to
inject to a patient.

Also
titration is very important in the pharmaceutical industry, where
precise measurements of quantities and concentrations are essential
throughout the manufacturing process. Titration is thus an important
part of the pharmaceutical industry to ensure quality control. Many
variations of the titration technique are used, and specialized
equipment for pharmaceutical titration is often developed to make the
process more efficient.

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