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Файл:English in Analytical Chemistry communicating about Methods & Techniques. Учебное пособие. Книга для студента
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23 Fill in the gaps for analyte, precipitating agent, or weighed form. Write the full
names for all the compounds involved. Formulate the coherent sentences for all
the cases using the props below.
Prompts. To determine magnesium, we apply… as a precipitating agent. The final
weighed form will be…
(based on B.M. Tissue – The Basics of Analytical Chemistry)
24 Study the flowchart and describe a typical procedure of a gravimetric analysis
using the key words provided.
Watching and Speaking
25 Watch the video “Gravimetric Analysis” and fill in the gaps. Make up 5
questions to the video. Discuss them in groups. To watch the video, follow the
link: https://disk.yandex.ru/i/HaHq4dWDWv0XCA
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Gravimetric Analysis
This is gravimetric analysis where you can [...] an unknown chloride. Accurately
weigh around […] of the unknown chloride using an [...]
[…] the solid in a hundred centimeters cubed of deionized water with three
centimeters cubed of nitric acid.
Add 20 centimeters cubed of silver nitrate solution until you see a [...]
Add a further 5 centimeters cubed of silver nitrate solution.
Heat the solution gently for 10 minutes without allowing it to [...].
Leave the solution to cool for at least 2 hours.
Next, accurately [...] some filter paper.
Fold the filter paper and put it in the filter.
The solution is now [...]
You are to [...] it into [...], you'll notice it's [...] a bit gray now as well.
Use the wash solution to wash out any remaining precipitate.
Test a used wash solution using [...]
What we're looking for is to see a precipitate form.
In this case it has.
So what you want to do is you want [...] with [...] more of wash solution and then
we'll test this wash solution again to see if it still precipitates.
Now I'm going to test the wash solution again.
We're still getting a precipitate, so we'll keep with [...] it until we no longer get a
precipitate and this [...]
All right, I'm going to test the precipitate again to see if it happens.
We are now not getting a precipitate; the solution [...] colorless, and there's no
cloudiness that would show a precipitate.
So, at this point we can take the filter paper and dry it [...].
Dry in a drying oven until a [...]
You check this by re-weighing it; once your [...] is completely dry, [...] on the right
weighing scales.
Vocabulary Boost
26 Match the words with their definitions.
1 coagulation A A coprecipitated impurity trapped within a precipitate
as it forms.
2 homogeneous
precipitation
3 relative
supersaturation
4 occlusion D A precipitation in which the precipitant is generated in
5 inclusion E The process by which a precipitate is given time to
6 precipitant F Any method in which the signal is a mass or change in
B A reagent that causes the precipitation of a soluble
species.
C The process of smaller particles of precipitate
clumping together to form larger particles.
situ by a chemical reaction.
form larger, purer particles.
mass.
22
7 gravimetry G
A
coprecipitated impurity that adsorbs to the surface of
a precipitate.
8 digestion H A measure of the extent to which a solution, or a
localized region of solution, contains more dissolved
solute than that expected at equilibrium (RSS).
9 adsorbate
I A coprecipitated impurity in which the interfering ion
occupies a lattice site in the precipitate.
27 Translate the following terms and gravimetry-related collocations from English
into Russian.
Mass alteration, to remove impurities, to determine target analyte, to meet the
requirement, to determine total suspended solids, to obtain a pure form, to calculate the
percentage, to use certified weight, to separate ions in a mixture, to oxidize iron to +3
oxidation state, to cool crucible in a desiccator, to choose a reagent selective for the
target analyte, to obtain a clear / cloudy solution, to remove excess of precipitating
agent, to work on the weighed form
28 Name the object or action using the pictures.
A Equipment Items
1 2
3 4
23
5 6
B Steps of Analysis
1 2
3 4
24
29 Give the full names to the typical gravimetric reagents.
1. AgCl
2. NH
4H2PO4
3. Mg2P2O7
4. Fe2O3
5. Fe(OH)
6. H2O
3
2
7. (COOH)2
8. CaO
9. H2SO4
10. PbSO4
11. AgCl
12. NH4H2PO
13. Mg2P2O7
14. Fe2O3
15. Fe(OH)
16. H2O
3
2
17. (COOH)2
18. CaO
4
20. AgCl
21. NH4H2PO
22. Mg2P2O7
23. Fe2O3
24. Fe(OH)
25. H2O
3
2
26. (COOH)2
27. CaO
28. H2SO4
29. PbSO4
30. NH4OH
31. Al2O
3
32. HCl
33. AgNO3
34. BaCl
35. BaSO
36. PO
2
4
3-
4
37. MgCl2
4
19. H2SO4
30 Give definitions to the words using the tag words provided.
Ignition, electronic balance, pure form, electrogravimetry, primary standards,
particulate gravimetry, addition, target analyte
Tag words: key step, to convert, equipment item, to measure, to weigh, to
transfer, electrode, certified weight, known concentration
31 Translate gravimetric steps and procedures from Russian into English.
1. высушивание
2. прокаливание
3. осаждение
4. добавление
5. удалить
6. добавить
7. промыть
8. повторно промыть
9. повторно взвесить
10. фильтрование
11. преобразование
12. обработка
13. охлаждать
14. нагревать
15. растворение
16. разбавление
32 Work in four separate groups and compile a bilingual self-made glossary using
the following building blocks. For each group, there must be at least four words
within each building block. Upload your result to Google Docs or any other
shareware. Prepare for a final credit on gravimetry.
1) Basic terms (=fundamental notions that define gravimetry as a method)
2) Purposes and objectives of gravimetry
3) Equipment in gravimetry
4) Gravimetric procedure steps and typical reagents
25
For additional practice, follow the link:
https://quizlet.com/415268021/gravimetry-flash-cards/
Check Yourself
1 Complete the text with the words from the box.
precipitation indirect measurements impurities particulate
quantitative volatilization
In a gravimetric analysis, a measurement of mass or a change in mass provides
1______________ information about the analyte. The most common form of gravimetry
uses a 2_____________reaction to generate a product whose mass is proportional to
the amount of analyte. In many cases the precipitate includes the analyte: however, an
3__________ analysis in which the analyte causes the precipitation of another
compound also is possible. Precipitation gravimetric procedures must be carefully
controlled to produce precipitates that are easy to filter, free from 4______________,
and of known stoichiometry.
In 5___________gravimetry, thermal or chemical energy decomposes the sample
containing the analyte. The mass of residue remaining after decomposition, the mass
due to the loss of volatile material are all gravimetric 6_____________.
When the analyte is already present in a particular form that is easy to separate from its
matrix, then a 7__________gravimetric analysis may be feasible. Examples include the
determination of dissolved solids and the determination of fat in foods.
(based on D. Harvey – Analytical Chemistry 2.0)
2 Guess the basic term by its definition using your self-made dictionary.
8. A method that identifies the amount of an analyte in a sample by weighing its
pure form.
9. A ratio of molecular weight of an analyte to molar weight of a pure form.
10. A process contrary to concentration.
11. A sample with a known concentration in a sealed container.
12. A synonym for the verb ‘to determine.’
13. ‘Solid particles’ in different words.
14. All the steps in your procedure.
15. When your method takes too much time, it is…
16. In gravimetry, mass alteration performs this function.
17. A process of transforming liquid into solid; one of the key steps in gravimetry.
3 Complete the gaps in the text below. The first letter is provided as a hint.
Gravimetric analysis describes a set of methods in a____18_____ chemistry
for the q_____19_____ determination of an analyte based on the mass of a solid. A
simple example is the measurement of solids suspended in a water sample: A known
v____20_____ of water is filtered, and the collected s____21_____ are weighed.
In most cases, the a______22_____ must first be converted to a solid by precipitation
with an a______23_______ reagent. The precipitate can then be collected by
f______24_______, washed, dried to r______25_____ traces of moisture from the
solution, and weighed. The amount of analyte in the original sample can then be
26
c_____26______ from the mass of the precipitate and its chemical
c_______27_________.
In other cases, it may be easier to remove the analyte by vaporization. The
analyte might be collected – perhaps in a cryogenic trap or on some
a______28________ material such as activated carbon - and measured directly. Or, the
sample can be w_____29______ before and after it is d_____30______; the difference
between the two masses gives the mass of analyte lost. This is especially useful in
determining the water content of complex materials such as foodstuffs.
25-30 Excellent. You can use the vocabulary from Unit 1 very well.
20-24 Quite good, but you need to learn some words.
10-21 Not bad, but you need to be more persistent in your everyday practice.
0-9 This is hard for you. Learn the vocabulary from the Unit 1 and do the tasks again
27
Unit 2
TITRIMETRY
Learning objectives
In Unit 2, you will learn to define basic terms and explain the principles of
titrimetry, learn the chief titrimetric types and techniques, and typical
titrimetric procedures.
The word "titration" descends from the French word tiltre
(1543), meaning the proportion of gold or silver in coins or
in works of gold or silver; i.e., a measure of fineness or
purity. Tiltre became titre, which thus came to mean the
"fineness of alloyed gold", and then the "concentration of a
substance in a given sample". In 1828, the French chemist
Joseph Louis Gay-Lussac first used titre as a verb (titrer),
meaning "to determine the concentration of a substance in
a given sample".
Joseph Louis Gay-Lussac
Warming up
1 Work with a partner. Draw the following equipment items and identify their
functions in titrimetry.
Buret [burette]; assembly kit; beakers for analyte and for titrant; Erlenmeyer flask /
rimmed flask / conical flask; small funnel, wash bottle with deionized water; buret clamp;
waste container; tip; stopcock; reading card; sheet of white paper; pipet bulb; volumetric
pipet; fume hood.
2 Work with the partner and formulate the basic facts for titrimetry as 3 separate
coherent sentences. Then answer the questions using your background in
chemistry and complete the basics.
1. Is it a qualitative or a quantitative method?
2. What is the general purpose for titrimetry?
3. How many solutions are used in titrimetry? How do they call them?
4. Is it a flash (=fast) or a time-consuming method?
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5. What are the analytical signals in titrimetry?
6. What is the the chief calculating operation?
7. Is it an accurate or inaccurate method?
8. What are the indicators used for? Name some of the indicators that you know.
9. What is aliquot? What is its function?
Reading and Speaking
3 Match the following terms with their definitions:
buret titrant endpoint indicator equivalence point
1. __________ The point in a titration where stoichiometrically equivalent amounts
of analyte and titrant react.
2. __________ A colored compound whose change in color signals the end point of
a titration.
3. __________ Volumetric glassware used to deliver variable, but known volumes
of solution.
4. __________ The reagent added to a solution containing the analyte and whose
volume is the signal.
5. __________ The point in a titration where we stop adding titrant.
4 Watch the first video on titrimetric procedure, fill in the gaps, and correct the
mistakes for the words capitalized. Follow the link:
https://disk.yandex.ru/i/iYlzGzoIsp-QAg
Vocabulary
Before watching, find the Russian equivalents of the words and word
combinations provided below.
Actions: to add by drop / to add dropwise; to adjust; to assemble; to do
something in triplicate; to mark; to mount; to record; to review; to rinse, to secure; to
swirl; to transfer; to regulate.
Additional words: concave / convex meniscus; initial volume / final volume; flow
of liquid, litmus; markings; spill hazard.
Preparing and Performing a Titration
Materials and Equipment Items. Hi! I'm Jared Heymann, an assistant professor
of chemistry at Elon University. Today, we will be discussing the proper titration
technique using the complete single […] available from Carolina's biological supply
company. This is the first in a two-part video series on titration. The GOAL of a titration
is to quantitatively determine the concentration of an unknown solution commonly called
the TITRANT, or analyte, by adding a volume of a chemical with a known concentration
called the titrant. To mark the end point of a titration, an indicator is added to the
analyte. Let's […] some of the equipment that's needed for a titration.
29
Carolina's complete burette assembly contains the basic equipment to get you
started, including a burette, a ring stand, and a burette clamp. A burette is a long narrow
[…] tube used to […] titrant; it has a stopcock to regulate […]. Notice that the
GRADUATIONS on the burette go from
lowest at the top to highest at the bottom. The
ring stand and burette clamp are used […]
your burette. Other materials you will also
need include a small funnel to help you fill the
burette; a 125 milliliter Erlenmeyer flask which
works best for titrations (the shape of the
flask allows for more vigorous swirling than a
beaker or other glassware and minimizes
[…]); a volumetric pipette and a pipette bulb
to transfer a known volume of analyte to the
flask; a wash bottle filled with deionized
water; a beaker or flask of titrant and of
analyte; indicators selected for your reaction; a reading card to help read the meniscus,
and a sheet of white paper to help […].
Preparation procedure. To prepare your burette for the titration, it is good
laboratory practice to rinse your burette CAREFULLY with deionized water, then with a
small amount of titrant. After each rinse, open the stopcock to allow the liquid TO DRY
at the bottom. If there is a lot of liquid CLEANING TO the walls of the burette, then
thoroughly clean your burette and repeat the rinse process. The accuracy of this
technique is dependent on the titrant flowing into the flask and not sticking to the walls
of the burette. Mount the burette […] making sure it is positioned vertically and there is
enough room to position your flask underneath the TOP. Check to see that the stopcock
is in the closed position. […] the funnel into the top of the burette and fill with titrant
almost to the top. Filling exactly to the zero mark is not necessary, but you do need
sufficient titrant TO TERMINATE the reaction. Check the column for […] and […] to free
them from the sidewalls. Remove the funnel, place the Erlenmeyer flask under the tip,
and open the stopcock to allow a few milliliters of titrant to flow through releasing any
[…]. Rinse the tip of the burette with water.
Performing a titration: start. Empty the liquid into a waste container and
thoroughly rinse the flask. It is not necessary to dry the flask. Record your INITIAL
VOLUME. It is important to accurately read the volume on the burette. First, note that
the liquid forms […] because the water pulls itself up the sidewalls of the glass. You
should read the volume from the bottom of the meniscus […]. Secondly, it is important
to read your volume to the correct number of significant figures. This burette indicates
volume to the nearest point 1 milliliters. With any graduated […], record the volume to
one additional decimal place beyond the smallest graduation. In this case record the
volume to the nearest hundredth of a milliliter EVALUATING the final place. Use the
volumetric pipette to TRANSFORM the analyte to the flask.
Add a few drops of indicator to the flask and […]. Place the flask under the tip of
the burette. Record this volume. Placing a piece of white paper under the Erlenmeyer
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