TITRATION USING NATURAL INDICATORS
Name: Kashvi
Roll No.
INDEX
Certificate
Acknowledgement
Aim
Materials & Apparatus
Theory
Types of indicators
Basic terms we should know before performing
titration
What is pH ?
Beetroot as an indicator
Onion as an indicator
Procedure
Preparation of beetroot indicator
Preparation of onion indicator
Observation
Calculation
Conclusion
Precautions
Source of error
Bibliography
Acknowledgment
I extend my deep sense of gratitude to Ms.
Sangeeta Bhowmik, whose constant
encouragement and supervision has made the
present work possible it is she who showed
nuances of this project and motivated me to go
for it. Her continuous guidance and supervision at
every stage of my project was a great boost for
me.
Secondly, I am indebted to Mr. Rohit, in charge
of the chemistry lab of the school, for providing
me with the equipment which were required to
perform this experiment pertaining to the project
mentioned earlier and for his help at each and
every stage of this project.
Certificate
This is to certify that Board Roll No: _____________ of
class 12th__ of Father Agnel School, New Delhi has
successfully completed his/her Chemistry Investigatory
project entitled “Natural indicators for titration” in the school
chemistry lab.
This work has been carried out under my supervision and
guidance. It is my pleasure that he/she has been able to
prepare the project within the stipulated time frame to my
utmost satisfaction.
The progress of the project has been continuously reported
and been in my knowledge consistently. The approach
towards the subject has been sincere and scientific.
Mr. Rohit Ms. Sangeeta CBSE
(Lab Assistant) (Chemistry Teacher)
Aim
To study the natural indicators for titration.
Materials Required
Conical flask
Burette
Burette stand
Pipette
White tile
Water bath
Tripod stand
Wire gauze
Ethanol
Beetroot
Onion peel.
Theory
Indicators are substances whose solutions change
color due to change in pH. These are called acid –
base indicators. They are usually weak acids or bases,
but their conjugate base or acid forms have different
colors due to differences in their absorption’s spectra.
Types of Indicators
[1] NATURAL INDICATORS
A natural indicator is a natural substance that can be
used to determine the pH of another substance.
For example: turmeric, beetroot, onion, red cabbage etc.
[2] SYNTHETIC INDICATORS
A synthetic indicator is a man-made chemical substance
used to determine pH.
For example: phenolphthalein, methyl orange, litmus etc.
Basic terms we should know before
performing Titration
VOLUMETRIC ANALYSIS: It involves determining
the quantities of a substance present in a given solution to
react quantitively with a solution of another substance of
known concentration.
TITRATION: Titration is a process in which a fixed
volume of solution is taken in a conical flask, another
solution of known concentration is added to it with the
help of a burette to bring about a definite reaction to
completion by reacting with the acid.
BASE – ACID TITRATION; Take a fixed volume of
dil.HCL of known concentration in a conical flask and
add 2-3 drops of indicator. Then add base from the
burette till the pink color disappears, it is called base-
acid titration.
ACIDITY OF A BASE: It is the number of OH ions
produced in aqueous solution.
BASICITY OF AN ACID: It is the number of
replaceable H+ ions present in an acid.
What is pH?
PH is a measure of the hydrogen ion activity, typically in
aqueous solution.
Acidic solutions have pH < 7. pH values lower than 0 are
possible.
Basic solutions have pH > 7. pH values greater than 14
are possible.
Beetroot as an indicator
Beetroot is a red glycosidic food dye obtained from its
aglycone, obtained by hydrolyzing the glucose molecule
betanin.
The color of betanin depends on pH. It is bright bluish red
becoming blue violet as the pH increases. Once the pH
reaches the alkaline levels betanin degrades by hydrolysis
resulting in a yellow brown color.
ONION AS AN INDICATOR
They have characteristic odor but when chopped and are kept
in dil. NaOH solution, they lose their odor. However, on
keeping the chopped onions in a dil. acidic solution, the
characteristic smell of onion is not lost.
Procedure
PREPERATION OF BEETROOT INDICATOR
Step 1: Crush chopped beetroot nicely to form a thick
paste
Step 2: Boil this paste with some water for about 5-7
minutes.
Step 3: Strain the indicator formed using a strainer.
Keep it cool down and come to room temperature so
that it can be used for titration.
PREPERATION OF ONION PEEL INDICATOR
Step 1: Take an onion and remove its peel
Step 2: Take its peel and crush it as far as possible
Step 3: Add some water to the crushed onion peel and
heat it in a water bath keep stirring it regularly
Step 4: Now carefully add ethanol to the water bath
heat more with constant stirring. A pink color indicator
is observed, strain it and keep it at room temperature so
that it cools down and can be used for titration.
Observations
[1] Titration using phenolphthalein indicator
S. No. Volume of Acid Burette Reading Volume of Base
(HCL) Initial Final (NaOH)
1
10 ml 15.4 25.9 10.5
2
10 ml 25.4 36 10.4
3
10 ml 16 26.4 10.4
Concordant Reading:
10.4
[2] Titration using beetroot indicator
S. No. Volume of Acid Burette Reading Volume of Base
(HCL) Initial Final (NaOH)
1
10 ml 0.7 12 12.3
2
10 ml 22.8 26 12.2
3
10 ml 36 48.2 12.2
Concordant Reading:
12.2
[3] Titration using onion indicator
S. No. Volume of Acid Burette Reading Volume of Base
(HCL) Initial Final (NaOH)
1
10 ml 0 12 12
2
10ml 13 24 11
3
10 ml 25 36 11
Concordant Reading:
11
CALCULATIONS
0.1M HCl
Dilution formula
M1V1=M2V2
12 X V1 = 0.1 X (100/1000)
V1 = 1/1200
= 0.0008L or 0.8 mL
V1= 0.8mL
0.1M NaOH
Molarity = W(NaOH) / [M(NaOH) X V (solution
in l)]
0.1M = W(NaOH)/ 40÷ (200/100)
W(NaOH) = 0.8 g
Therefore, weigh 0.8 g of NaOH and dissolve it in
water to make it up to 200 mL.
CONCLUSION
1)A color change was observed in strong acid strong
base titration.
2)When the titration was conducted using beetroot as
the indicator, the color of the acid changed from
colorless to light pink.
3)When the titration was conducted using onion peel
as the indicator the color of the acid changed from
colorless to light yellow
4)
Precautions
1) Usually, an air bubble is present at the
nozzle of the burette, it must be removed
before taking the initial reading.
2) There should not be any leakage from the
burette during titration.
3) Keep your eye level with the liquid surface
while taking the burette reading or while
reading the pipette or measuring flask etc.
4) Always read lower meniscus in case of
colorless solution and upper meniscus in
case of colored solutions.
Sources of Error:
1) Misjudging the color of the indicator near the
end point, this is probably the most common
one Sometimes color change is delicate and
slow and not everyone has the same sensitivity
to colors.
2) Transferring of two different solutions using
a same pipette and not rinsing pipette with
distilled water in between.
Bibliography
1. Saraswati chemistry laboratory manual.
2. SlideShare.net/sudeera22/beetroot-as-an-
indicator.
3.www.chemicool.com
4.www.brainly.in
5.www.quora.com
