N/10 Sodium Thiosulfate Solution Preparation and Standardization with K2Cr2O7 | Iodometric titration
Summary
TLDRThis video tutorial demonstrates the preparation and standardization of sodium thiosulphate solution using potassium dichromate. The process involves weighing 2.48 grams of sodium thiosulphate and diluting it to 100 ml, followed by preparing a potassium dichromate solution with 0.49 grams in 100 ml. The video then details the titration process, including the addition of potassium iodide and HCl, and the use of starch indicator to determine the endpoint. The final step shows how to calculate the normality of the sodium thiosulphate solution and prepare an n by 80 hypo solution by dilution.
Takeaways
- 🧪 Sodium thiosulfate solution is prepared by weighing 2.48 grams of pentahydrated sodium thiosulfate and dissolving it in 100 ml of distilled water.
- 🔬 The prepared sodium thiosulfate solution is standardized using potassium dichromate, with 0.49 grams of potassium dichromate dissolved in 100 ml of distilled water.
- 🧼 All glassware, including burets and conical flasks, must be thoroughly rinsed before use to ensure accurate results.
- 📏 The titration process involves filling the buret with sodium thiosulfate solution and transferring 25 ml of potassium dichromate to a conical flask.
- 🧴 Potassium iodide and concentrated HCl are added to the potassium dichromate solution, which liberates iodine and changes the solution's color.
- 🧫 The titration continues by adding sodium thiosulfate to the flask until the dark brown color fades, followed by starch solution to form a starch-iodine complex.
- ⚗️ The titration is complete when the iodine's blue color disappears, and a pale color appears due to chromium ions.
- 📊 Observations include an initial buret reading of 0 ml and a final reading of 25 ml, indicating that 25 ml of sodium thiosulfate was consumed.
- 📝 The normality equation (N1V1 = N2V2) is used to calculate the normality of sodium thiosulfate, confirming it as N/10.
- 🌡️ To prepare N/80 sodium thiosulfate, 12.5 ml of N/10 sodium thiosulfate is diluted in a 100 ml measuring flask using distilled water.
Q & A
What is the purpose of preparing a sodium thiosulphate solution in the video?
-The purpose is to prepare a sodium thiosulphate solution and standardize it using potassium dichromate.
How much sodium thiosulphate is used to prepare the solution in the video?
-2.48 grams of sodium thiosulphate pentahydrate is used.
What is the final volume of the sodium thiosulphate solution prepared in the video?
-The final volume of the sodium thiosulphate solution is 100 ml.
How is the sodium thiosulphate dissolved in the video?
-It is dissolved by transferring the weighed amount to a measuring flask, rinsing the beaker properly, and shaking well to dissolve it into distilled water.
What is the concentration of the prepared sodium thiosulphate solution in the video?
-The concentration of the prepared sodium thiosulphate solution is n by 10.
How much potassium dichromate is used to prepare its solution in the video?
-0.49 grams of potassium dichromate is used.
What is the volume of the potassium dichromate solution prepared in the video?
-The volume of the potassium dichromate solution is 100 ml.
Why is it necessary to rinse the glassware before standardizing the solution in the video?
-Rinsing the glassware is necessary to ensure that there is no contamination that could affect the accuracy of the standardization process.
What is the initial reading of the burette when potassium dichromate is added in the video?
-The initial reading of the burette is zero.
How much potassium iodide is added to the conical flask in the video?
-0.5 grams of potassium iodide is added to the conical flask.
What color change is observed after adding concentrated HCl to the conical flask in the video?
-After adding concentrated HCl, the color changes to indicate the liberation of iodine.
How is the endpoint of the titration determined in the video?
-The endpoint of the titration is determined by the disappearance of the color of the starch-iodine complex after adding a few drops of starch solution.
What is the final reading of the burette after the titration in the video?
-The final reading of the burette is about 25 ml.
How is the normality of the sodium thiosulphate solution calculated in the video?
-The normality is calculated using the normality equation N1V1 = N2V2, where N1 and V1 are the normality and volume of potassium dichromate, and N2 and V2 are the normality and volume of sodium thiosulphate.
What is the normality of the hypo solution prepared by dilution in the video?
-The normality of the hypo solution prepared by dilution is n by 80.
How much volume of n by 10 sodium thiosulphate solution is taken to prepare n by 80 hypo solution in the video?
-12.5 ml of n by 10 sodium thiosulphate solution is taken to prepare 100 ml of n by 80 hypo solution.
Outlines
🧪 Preparation of Sodium Thiosulphate Solution
In this section, the process of preparing sodium thiosulphate solution is explained. The speaker weighs 2.48 grams of sodium thiosulphate, transfers it to a measuring flask, and dissolves it in distilled water. After ensuring it is well mixed, the solution is made up to 100 mL. The prepared solution is of n/10 concentration, and the sodium thiosulphate used is pentahydrated.
🔬 Preparation of Potassium Dichromate Solution
This paragraph details the preparation of potassium dichromate solution. The speaker uses 0.49 grams of potassium dichromate, dissolves it similarly by rinsing a funnel, and transfers the dissolved solution into a flask. After dissolving it fully, the solution is made up to 100 mL and shaken well to ensure homogeneity.
🧴 Preparing the Equipment for Standardization
Before starting the titration, the speaker stresses the importance of thoroughly rinsing the glassware, including the buret and conical flask, to ensure accuracy. Sodium thiosulphate solution is used to rinse the buret, and potassium dichromate is used to rinse the conical flask, following which 25 mL of potassium dichromate solution is added to the flask.
⚗️ Adding Reagents for Titration
After preparing the potassium dichromate solution, the speaker adds 0.5 grams of potassium iodide to the conical flask, followed by 1 mL of concentrated hydrochloric acid (HCl). This results in the liberation of iodine, indicated by a change in color. The flask is then covered with brown paper to prevent exposure to sunlight, which could oxidize the iodine.
🧪 Conducting the Titration Process
The speaker begins the titration by adding sodium thiosulphate solution from the buret into the conical flask containing the iodine. After the solution turns light brown, a starch solution is added, creating a blue-black iodine-starch complex. As titration continues, the color disappears, marking the endpoint. The speaker notes that the remaining slight color is due to chromium ions.
📊 Observation and Normality Calculation
This part describes the observation table, with the initial buret reading at 0 mL and the final reading at 25 mL, indicating 25 mL of sodium thiosulphate was used. Using the normality equation (N1V1 = N2V2), the speaker calculates the normality of the sodium thiosulphate solution. Since both solutions are of n/10 concentration, the normality of the sodium thiosulphate is confirmed to be n/10.
📏 Preparation of n/80 Sodium Thiosulphate Solution
In this paragraph, the speaker explains how to prepare an n/80 sodium thiosulphate solution using the dilution method. They take 12.5 mL of the standardized n/10 sodium thiosulphate solution and dilute it to 100 mL with distilled water. This produces an n/80 solution, which is achieved through careful measurement and calculation.
👍 Conclusion and Final Remarks
The speaker concludes the video by summarizing the successful preparation of n/10 and n/80 sodium thiosulphate solutions. They encourage viewers to like, share, and subscribe if they found the content helpful, offering thanks for watching the video.
Mindmap
Keywords
💡Sodium Thiosulphate
💡Standardization
💡Potassium Dichromate
💡Titration
💡Normality
💡Potassium Iodide
💡Concentrated Hydrochloric Acid (HCl)
💡Starch Solution
💡N/80 Hypo Solution
💡Chromium (III) Ions
Highlights
Preparation of sodium thiosulphate solution by weighing 2.48 grams of sodium thiosulphate pentahydrate.
Solution made by transferring the sodium thiosulphate into a 100 mL measuring flask and dissolving it in distilled water.
Potassium dichromate solution preparation by dissolving 0.49 grams of potassium dichromate in 100 mL of distilled water.
Importance of rinsing all glassware thoroughly before use to ensure accuracy during standardization.
Filling the buret with sodium thiosulphate solution after rinsing it multiple times to avoid contamination.
Potassium dichromate solution transferred into the conical flask for titration, starting with 25 mL.
Addition of 0.5 grams of potassium iodide to the conical flask, followed by 1 mL of concentrated HCl to liberate iodine.
Titration process with sodium thiosulphate to reduce iodine until the dark brown color fades.
Addition of starch solution during titration, creating a starch-iodine complex and a visible color change.
Completion of titration when the blue-black color of the starch-iodine complex disappears.
Observing final titration reading of 25 mL, equating to full consumption of sodium thiosulphate solution.
Calculation of the normality of sodium thiosulphate solution using the equation N1V1 = N2V2.
Preparation of N/80 sodium thiosulphate solution by dilution method from standardized N/10 solution.
Using 12.5 mL of N/10 sodium thiosulphate solution and diluting it to 100 mL to achieve N/80 concentration.
Reiterating the process of solution preparation and standardization, ensuring proper methodology and accurate results.
Transcripts
everyone welcome back to Spectrum
classes
today in this video we are going to
prepare sodium thiosulphate solution
as well as its standardization with the
help of potassium dichromate so here I
am going to prepare the sodium
thiosulphate solution for that I have
taken 2.48 grams of
sodium thiosulphate now I am preparing
the solution so the weight amount you
have to transfer to the
measuring flask
now rinse your final properly
and shake it well
to dissolve the sodium thiosulphate
into the distilled water and now once it
is dissolved you make up the solution up
to the mark which is given over there
and the solution is 100 ml the
calculation which we have done is 400 ml
so this is how we can prepare
sodium thiosulphate solution
here it is as weighed and calculated n
by 10 sodium thiosulphate
and this sodium thiosulphate is
pentahydrated now we are going to
prepare potassium dichromate solution
and for that purpose I have taken 0.49
grams of potassium dichromate
now I transferred it again in the same
way and now I am going to rinse this
funnel properly
and thoroughly
now I am going to dissolve this
potassium dichromate
so you see it is not completely
dissolved so you have to dissolve it
first
once it is dissolved you make up the
solution up to the mark and this
solution is 100 ml
after
making it up up to the mark you shake it
well
before use
now we are going to rinse the glass
layers because we are standardizing so
every glassware should be washed
thoroughly and it is rinsed before using
so in the buret I am going to fill the
sodium thiosulphate solution so I am
rinsing it with the help of sodium
thiosulphate solution
now I fill it after rinsing two three
times you take
little more amount in the buried just to
fill this nodule now I am going to rinse
conical flask also
with the potassium dichromate as I am
going to take potassium dichromate in
the conical flask
and now I am going to transfer 25 mL of
potassium dichromate
in the conical flask and this potassium
dichromate solution is of n by 10
concentration
initial reading of the buret is zero
we are going to add this
potassium dichromate solution in the
conical flask now I am going to add
potassium iodide
to this
0.5 grams to the conical flask
and now I am shaking it you see no color
changes visible now I am going to add
one ml of concentrated HCl solution to
this conical flask and you see the color
iodine is liberated now let this conical
flask with the help of a petri dish I am
showing you the color but before doing
the titration you keep it with a wrapped
brown paper just to avoid the exposure
of this conical flask
from the direct sunlight because that
can oxidize this iodine
now titrating it against the sodium
thiosulphate solution
and we first do this titration until
this dark brown color get it painted
now we are going to add
starch solution to this two three drops
I'm adding three four drops actually so
you see the color
of starch iodine complex now we are
again titrating it and on titration you
see
the color disappears this I am shaking
it just to ensure that the iodine is
titrated and see later on you will see
this type of color so you may get
confused
titration is completed or not actually
this is because of the chromium 3 plus
ions
now take the final reading of the buret
which is about 25
M now calculate the concentration
now coming to the observation table here
in observation table
I have kept the volume taken for k2cr207
is 25 ml which is taken in the conical
flask initial reading of the buret is 0
and final reading of the view rate is 25
ml
so on subtracting this final to initial
we get 25 mL of sodium thiosulphate is
consumed
now calculation using the normality
equation so N1 V1 is equal to n2b2 here
this side I have chosen k2cr2o7 and on
this side I have chosen sodium types
on putting the values of these N1 V1
normality and volume
on each sides so N1 is
n by 10 for k 2 cr207 which I have
prepared by calculation and since it is
a primary standard so it is suppose that
the weight we have taken is exactly at
the same normal solution and against
this 25 mL of n by 10 K to cr207 25 mL
of two sodium thiosulfate is consumed
now calculating the normality of sodium
thiosulphate which we have prepared this
will be canceled out by this so
normality of sodium thiosulphate is n by
10 which we prepared
baby this is the result now coming to
the preparation of n by 80 hypo solution
so this n by 80 hyper solution will be
prepared by dilution method and here we
are again using this normality equation
so I want to prepare n by 80 sodium
thiosulphate solution and in 100 ml so
whatever volume you want to prepare you
can put that volume here this equal to
stock solution so stock solution is n by
10 now which we have standardized Now
volume of this is standardized
hypersolution taken to prepare this
solution in 100 ml so on calculation I
will get that 12.5 mlo hyper solution of
n by 10 normality is taken in 100 ml to
prepare n by 80 hypo Solution by this
dilution method so we come to know that
the sodium thiosulphate solution which
we have prepared by being is about n by
10 normality so we are going to prepare
and by 80 Solution by dilution method so
for that purpose I am going to take 12.5
ml of sodium thiosulphate which is
already filled in the buried to this
measuring flask
on adding 12.5 mL of and by 10 sodium
thiosulphate solution to this measuring
plus I will stop this
and
you see the reading so I after
calculation I have done this
and this is 12.5 ml in this measuring
class now I am going to make up the
solution up to the mark by distilled
water
this measuring flask is of 100 ml
so this is how we can prepare n by 80
sodium thiosulfate Solution by dilution
method from The Strand rice n by 10
sodium thiosulphate solution
if you find this video useful please
like share and subscribe thank you all
thanks for watching
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