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Файл:English in Analytical Chemistry communicating about Methods & Techniques. Учебное пособие. Книга для студента
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flask may make it easier […] the color change. WORKING the burette requires two
hands: one hand turns the stopcock while the other hand swirls the flask. Practice
turning the stopcock a few times to familiarize yourself with how quickly the flow starts
and stops. It is common laboratory practice that the first titration is an estimate. Open up
the stopcock and allow the titrant to enter the flask quickly. Continuously swirl the flask.
As the volume of titrant in the flask increases, the color of the indicator appears and
then disappears as you swirl.
Performing a titration: end. When the analyte becomes a colored solution,
close the stopcock. Record the final volume of the burette. Subtract the initial volume
from this final volume to get the estimated volume of titrant needed for this titration.
Knowing the volume, that is a little past the […], subtract 5 milliliters from that number to
get the amount of titrant that can be safely added before a slower […] is required. As
the estimate titration shows, a dark colored solution indicates an excess of titrant has
been added. The desired end point is a pale, faintly colored analyte. To reduce the risk
of passing the end point, slow down the addition of titrant when flashes of color begin to
appear in the analyte. ADAPT the stopcock to slow the flow of titrant to a drop-wise
SPEED. Continue to swirl the flask with one hand and keep the other hand ready to
close the stopcock. When you notice the indicator taking longer to fade, close the
stopcock. Rinse the tip of the burette with deionized water and swirl the flask. Record
the final volume on the burette. If the analyte […] faintly colored, then you have reached
the end point. If the analyte is still colorless, then repeat these steps: add a drop, rinse,
swirl, and record until a faint color persists. Typically, titrations are performed in
triplicate. Use the average volume of the titrant required to reach the end point for any
calculations. You now know how to properly perform a titration.
Be sure to check out the second video in this series. In that video we will go over
the […] for determining the concentration of an unknown acid solution using a base of
known concentration. Carolina has everything you need for your chemistry lab. Visit us
at carolinachemistry.com to see our complete line of products and kits for chemistry.
(Based on carolinachemistry.com free videos)
5 Now answer the questions to the video script.
1. What is the purpose of titration technique?
2. What are the two chemicals [solutions] used for titration?
3. What is the function of indicators?
4. List the equipment used for titration.
5. What do we need to rinse the burette for?
6. What are we supposed to do we do after we rinse the burette?
7. What do we need to check for the burette?
8. Why do we need to open the stopcock?
9. What value do we need to record after we empty the liquid into the waste
container?
10. What is the function of volumetric pipette?
11. What are we supposed to do after the indicator is added?
12. What do we do after we see the change of color (2 things)?
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13. How do we recognize the end point?
14. What are the four actions that we need to repeat if the analyte is colorless?
15. How many times do we perform titrations?
6 Prepare for the individual talk with your teacher based on the video questions.
Vocabulary Boost
7 Choose a common word for each group to get collocations.
a) equivalence ..............
end.............
b) .............curve
.............error
c) ................... indicator
....................titration
d) ................ oxidizing…….
................. reducing……
................. complexing……
e) acid-base ..............
argentometric ..............
complexation ..............
displacement..............
precipitation..............
redox..............
8 Give definitions to the terms below following the prompt in the box.
Giving definitions
A is B that C
• A solute is a substance that is dissolved in another substance, known as
solvent.
• Solution is a homogeneous mixture that is composed of two or more
substances.
curve _________________________________________________________________
displacement___________________________________________________________
stopcock______________________________________________________________
detect_________________________________________________________________
titrand_________________________________________________________________
9 Relying on the video script, draw the academic vs. chemistry mind map for the
equipment items, actions, and additional words related to titrimetry (look for the
words in ex. 1, 3, and 4 above).
1. Divide the words into two columns: “Academic” – for the generic terms that
could be used outside the scope of analytical chemistry – and “Chemical” – for specific
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terms that reflect certain aspects of AC (types of analysis, methods, typical actions,
etc.).
2. Provide a simple English synonym for each word if it is possible. If not, draw a
schematic picture to visualize the word or download an associative picture from the
Internet (if you decide to make the mind map in e-format). Make sure all of the words
are put into their root forms.
Academic words are generally used in a scientific context and suit various
areas of science – whereas chemistry terms are used in a specific chemistry-oriented
context only. If it is difficult for you to remember a simple synonym, resort to
https://www.thesaurus.com/ or https://context.reverso.net/. However, do not use for
synonyms the words you do not know yet!
Example:
ACADEMIC CHEMICAL
INITIAL VOLUME = STARTING VOLUME BURETTE
10 Vocabulary boost: imagine. Think of a word from the mind map you have
devised. Prepare several riddles or puzzles via Power Point Presentations or
simply by doodling pictures in your copybooks. Make your co-students work out
the words relying on the visual prompts.
11 Vocabulary boost: guess. Look at the riddles below. Work out which word or
word combination it stands for.
1.
ACADEMIC
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2.
3.
1
CHEMICAL
34
2.
3.
12 Translate the statements into English.
1. Титрование – это относительно экспрессный метод количественного
анализа, аналитическим сигналом в котором является изменение объёма.
2. В сравнении с гравиметрией титрование – менее точный и затратный по
времени метод.
3. Оборудование и материалы, применяемые в гравиметрии, включают в
себя бюретку, пипетку-грушу, волюметрическую пипетку и аликвоту.
4. Набор для титрования собирается и устанавливается для
последующего проведения анализа.
5. Экран используется для визуализации конечной точки титрования.
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13 Look at the pictures and describe how a titration is performed. Work in groups
of three or four. Look at the pictures and describe how the titration is performed.
Part 1. Setting up Your Equipment
Part 2. Conducting Your Titration
36
f
Part 3. Finishing Your Analysis
14 Match the terms with their definitions
1 Titrant
A empirical reflection of equivalence point
2 Titrimetry (titrimetric method)
B occurs because of the difference between
equivalence point and end point
3 Titre
4 Titrand (=titrated analyte)
5 To titrate
6 Signal
7 Back titration
8 Displacement titration
9 Direct titration
C one of analytical methods that implies the
determination of an analyte quantity via alteration o
a titrant volume
D the solution / the soluble substance with unknown
concentration
E the solution with the known concentration applied
to determine the volume, hence, we can calculate
concentration or mass of a titrated analyte
F to conduct the process of titration
G ratio of a solute mass to a solution volume
expressed via mL
H for this technique, one needs to add excessive
solution with definite concentration and to titrate the
residual titrant with another solution
I any kind of visible / observable change that we use
for analysis
10 Titration curve
J one needs the supplementary reagent for this
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technique
f
11 Equivalence point
12 Endpoint
13 Titration error
K graphically expressed dependence (=function) o
pH to a titrant volume (in acid base titration)
L the point on a titration curve where the quantity of
a titrant equals the quantity of a titrated analyte
M for this technique, only titrant is required
15 Now resort to any Russian reference guide in analytical chemistry (you might
use your lectures), find definitions for the terms in the previous exercise and
translate them into English in writing. Work in groups and exchange / compare
the definitions you have found; ask your partner to translate your versions into
English. Discuss the difficulties you encounter while translating from Russian
into English.
16 Fill in the gaps in the statements below.
1. Endpoint is the empirical reflection of...
2. Titration... occurs because of the difference between... point and endpoint.
3. Titrimetry is one of... that implies the determination of an analyte... by... of a titrant
volume.
4. Titrant is a solution with... concentration we use to...
5. Titre is the ratio of a... mass to a... volume.
6. Titre is expressed in...
7. In back titration, we add... solution and titrate the... titrant with another solution.
8. To conduct displacement titration, we apply... reagent.
9. The equivalence point shows that the amount of... is equal to...
10. In... titration, we apply only titrand and titrated analyte.
17 Define the analytical purpose for the terms in the chart below. Speak on the
spot without preparation. Use the prompts to talk about functions in the box.
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Equipment General terms General terms
A
Burette Titration Equivalence point To mount the
Volumetric pipette Direct titration Titre To secure the
Erlenmeyer /
rimmed flask
Stopcock Displacement
Reading card Titrant Titration error To empty the liquid
Indicator Titrated analyte Initial volume To swirl the burette
Litmus Volume Final volume To adjust the
Phenolphthalein End point Analytical signal To rinse the
18 Complete the definitions in B for the terms in A.
Back titration To titrate To visualize end
Titration curve To complete
titration
ctions
burette
burette
point
titration
into the waste
container
stopcock
burette carefully
A B
indicator A colored … whose change in color signals …
alkalinity A measure of a water's ability to …
acid-base titration
acidity A measure of a water's ability to …
Gran plot A linearized form of ...
Kjeldahl analysis An acid-base titrimetric method for …
conditional formation
constant
auxiliary complexing agent A second ligand in a complexation titration that …
buret ... used to deliver variable, but known volumes of
complexation titration A titration in which …
redox titration A titration in which …
auxiliary reducing agent A reagent used to reduce the analyte before …
auxiliary oxidizing agent A reagent used to …
formal potential
redox indicator A visual indicator used to signal …
precipitation titration A titration in which ...
argentometric titration
A titration in which …
The equilibrium formation constant for …
solution.
The potential of a redox reaction for a specific set of
solution conditions, such as …
A precipitation titration in which …
Discussion
19 Work in microgroups. Choose one of the four parts of the video in exercise 4:
Materials and Equipment; Preparation; Performing: Start; or Performing: End.
Edit the fragment to make it simple: Draw the pictures to visualize your fragment.
Make up questions to the fragment.
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How to simplify your fragments:
1) highlight the important words using your favorite color;
2) cross out the unnecessary words that do not add to the sentence;
3) replace some of the words with simpler synonyms if needed;
4) change Passive Voice to Active Voice if applicable;
5) split long complex sentences into several simple ones;
6) leave only instructive verbs and objects (e.g., add titrant. Use “Gravimetric
Determination of Iron” as an example);
7) omit the details that are uncommon to your laboratory practice.
Prepare to deliver your fragment in front of the group. Take different roles:
Painter (visualizes what the speaker is saying), English speaker (actually speaks),
English-into-Russian translator (translates every phrase into Russian), and
Questioner (prepares the questions to ask audience after the speech).
20 Work in groups of three and discuss the situations below.
1. During a titration, chemist may rinse inside of conical flask with
distilled or deionised water. Explain why it is important
2. During a titration chemist may rinse inside of chemical flask with
distilled water. Explain why this does not give an incorrect result
3. Suggest one source of error in using the burette to carry out
titration
4. Why equilibrium point pH is higher with a strong base, weak acid?
5. Why weak acids and weak base reactions are not used for titrations?
6. What happens if you add NaOH to an acidic buffer?
7. When titrating citric acid, the student added alkali dropwise. After some time, the
contents of the flask acquired a blue color, instead of crimson. Why did this happen?
21 Prepare a two minute long speech on a certain indicator. Mention its history,
practical application in analytical chemistry, color transitions in different media,
and your personal experience of working with it (if applicable).
Prompts to use
The history of this indicator dates back to… and is connected with the name of…
This indicator was discovered / developed by…
It is normally applied for…
Its color transition varies between…
In acidic / basic / neutral medium, it is…
Within pH range of…, it varies from… to...
I have worked with this indicator to…
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