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Title: pH indicators- research paper
Description: Research Question How accurate are natural indicators such as red cabbage, carrot, red chard, blueberries, cranberries and grape extract in determining the pH value of a substance?
Description: Research Question How accurate are natural indicators such as red cabbage, carrot, red chard, blueberries, cranberries and grape extract in determining the pH value of a substance?
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Centre: Kolej MARA Banting
Number of pages: 11 pages
Research Question
How accurate are natural indicators such as red cabbage, carrot, red chard,
blueberries, cranberries and grape extract in determining the pH value of a substance?
Introduction
Acid or bases are almost everywhere and we encounter them everyday even
most of the foods we consume are slightly acidic or basic
...
Numerous human body
processes involve acid-base reactions
...
Saliva, blood, and tears equitably neutral while stomach acid are highly acidic
...
Anything that
come into contact with concentrated acid or base can burn or corrode
...
Most of the household cleaners are
made from strong bases to eradicate oily soils
...
Vinegar and soda are both acids but are week that is not strong
enough to corrode things
...
The indicators that can be used to determine the pH level are litmus
paper, pH meters, and pH paper
...
Thymol blue, methyl red, bromothymol blue, and phenolphthalein are common
chemical indicators used in lab
...
However, due to the absent of
lab materials and apparatus, it is hard to determine pH level of household substances
at home
...
I remembered of a science
show on television about natural indicators can be used to measure whether a
substance is acidic or alkali
...
The
colour of the pigment differs in different pH as the colour is pink in acidic, purple
when neutral and greenish-yellow in alkaline
...
Muscle window and glass cleaner
500ml
Sprite carbonated drink
500ml
0
...
1M NaOH
500ml
Table 2: Apparatus
Apparatus
Quantity
Beakers (500mL)
5
Volumetric Flask (250ml)
6
Bunsen Burner
2
Tripod Stand
2
Wire Gouge
2
Asbestos
2
1 What are some natural acid/base indicators? (n
...
Retrieved February 21, 2016, from
http://antoine
...
edu/chem/senese/101/acidbase/faq/natural-indicators
...
Muscle window and glass
cleaner, sprite carbonated drink
b) Volume of indicators Use 80ml of red cabbage extract,
used in method part blueberries extract, grape skin extract,
B
red chard extract, cranberries extract,
carrot extract
c) Concentration of HCl 0
...
1 M NaOH is added drop by drop
in stopping at each colour change
method part B
e) Mass of fruits use as Make an extract of 200g of red
indicator
cabbage, red chard, grape, cranberries,
blueberries, carrot
3
Methodology
A
...
200g of red cabbage are boiled in 500ml of water until the color is drained
from the cabbage leaves
...
Repeat for all the indicators, carrot, red chard, grape, cranberry and
blueberry
...
Establishing a color scale for each indicator
1
...
2
...
1 M HCl are added drop
by drop, stopping at each colour change
...
The pH level of each color change for red cabbage is recorded
...
Step 1 to 3 are repeated for all natural indicators
...
The red cabbage extract is poured into another container and the starting pH
is measured
...
The pH meter is left in the container and drops of 0
...
7
...
8
...
9
...
10
...
C
...
50ml of white vinegar is poured into a container and its pH level is
measured with the pH meter
...
Red cabbages extract are added until the colour stops changing
...
Steps 1 and 2 are repeated for all other indicators that are not discarded
...
4
...
Tabulation of data
Table 4: Establishing a colour scale for each indicator
Type of
indicators
Red cabbage
extract
Grape’s skin
pH level
Colour
6
...
3
4
...
1
7
...
5
9
...
2
12
...
3
13
...
3 (Tested with
sodium hydroxide)
8
...
2
Light purple
2
...
7
5
...
2
>7
...
1 (Tested with
sodium
7
...
2
7
...
1
Effectiveness
Purple
Reddish purple
Red
Colourless
Turquoise
Greenish blue
Dark green
Green
Yellowish green
Yellow
Pale tan
Yellowish orange
Gold
Effective with wide range
Effective with small range
Red
Dark red
Darker red
Dark Grey
Black
Pink
Olive
Dark Olive
Forest Green
Orange
Effective with small range but
larger than grape
Effective with subtle change in
colour
Ineffective
Ineffective
5
Table 5: Determining the accuracy of the indicators
Substances
pH
level
Red
Cabbage
Cranberry
Blueberry
Grape skin
Estimated
pH level
%
Error
Vinegar
2
...
0
10%
Lemon juice
2
...
0
23%
Grape’s juice
2
...
0
10%
Albumin
8
...
0
6%
Sodium
bicarbonate
7
...
5
5%
Clorox
9
...
5
Purplish
pink
Unchanged
Unchanged
Unchanged
4
...
5%
Greenish
blue
Greyish
blue
Calculation
Percentage error = Estimated pH – Actual pH
______________________________ x 100
Estimated pH
3
...
7
×100
Percentage error = 3
...
A conclusion can be made that they must have low anthocyanins pigment
...
Grapes, blueberries and cranberries are naturally acidic therefore
they are only able to change colour in solutions, which are more basic than them
...
The pH level of a lot of the substances are difficult to determine by using the
natural indicators as the colour of indicators produce did not match the color scale
generated in part B of the experiment
...
All those 3 substances turned red cabbage to bubble-gum pink
when tested
...
30
...
A solution for this problem is to use several more indicators
that have a neutral pH originally therefore can cover both acidic and basic range
...
Due to the chemical in the substances
and the pH level of the substances are not in the range of the natural indicators,
unexpected colour appeared when tested
...
There is a pigment present in the indicators called anthocyanin
...
The
pigment is responsible to make many of the flowers and fruits to have red, blue and
purple colour
...
This is due to the presence of
anthocyanin in them
...
Anthocyanins are able to receive and remove hydroxyl group
...
On the other hand, if anthocyanin is mix with a basic solution, hydroxyl
group will be added to the molecules
...
The lower the pH of the solution will increase the concentration of hydrogen ions
...
Further decrease in pH value will cause quinodial bases to lose
another proton producing phenolate anion
...
The result from this, the green region in flavylium cation will have
a maximum absorption shifts to yellow linquinodial bases then to orange in phenolate
anion
...
Without
the presence of metal ion, the colour of anthocyanin in acidic solution would be red
meanwhile the colour of anthocyanin in basic solution is blue and in a neutral pH, it
will have purple colour
...
Abundance of anthocyanin
compounds exists in nature that forms the series
...
Gaining or losing hydroxyl group will alter the wavelengths at which the indicator
absorbs and reflects light
...
, Horner, G
...
, & Tarcy, D
...
Chemistry: Course companion
...
3 Re: What physical properties of Red Cabbage juice allows it to be an indicator? (n
...
Retrieved
February 21, 2016, from http://www
...
org/posts/archives/1998-03/890795428
...
r
...
Based on the pH
scale established, the natural indicators are then be used to discover the pH level of
household items
...
The pH level
of bleach cannot be determined as it is not in the range of the natural indicators
...
It is affordable and safe to be conducted in home environment
...
It is possible to determine the approximate pH of a solution with the range
from 1-14 as it displays variety of colours
...
It is difficult to determine estimated pH range of acidic substances due to only
one indicator that can be use, which is red cabbage
...
d
...
wikipedia
...
svg
9
2
...
In order for the results achieved to be more accurate, more trial should be
conducted for Part B and C of the experiment
...
Another natural indicators that
could be use are apple skin, hydrangeas, strawberry and beetroots
...
2
...
Further investigation
Use spectrophotometer to compare the colour changes therefore can produce more
accurate colour scale
...
Natural pH indicators are not pure as there are many other compounds in the
indicators
...
Overshooting of pH value as a tiny drop of acid can change the colour of the
indicator quickly thus give inaccurate result
...
Determination of colour might not be accurate as the colour of the natural
indicator is not so intense
...
, Horner, G
...
, & Tarcy, D
...
Chemistry: Course
companion
...
Website
(n
...
Retrieved October 21, 2015, from
https://en
...
org/wiki/Anthocyanin#/media/File:Anthocyanidine
...
d
...
frostburg
...
shtml
Use Garden Plants and Household Chemicals To Test pH Yourself
...
d
...
about
...
htm
Natural pH-Indicators
...
d
...
erowid
...
html
PH Indicators
...
Retrieved February 21, 2016, from
http://chemwiki
...
edu/Physical_Chemistry/Acids_and_Bases/Case_Studies/Aci
d_and_Base_Indicators/PH_Indicators
Re: What physical properties of Red Cabbage juice allows it to be an indicator? (n
...
Retrieved February 21, 2016, from http://www
...
org/posts/archives/199803/890795428
...
r
Title: pH indicators- research paper
Description: Research Question How accurate are natural indicators such as red cabbage, carrot, red chard, blueberries, cranberries and grape extract in determining the pH value of a substance?
Description: Research Question How accurate are natural indicators such as red cabbage, carrot, red chard, blueberries, cranberries and grape extract in determining the pH value of a substance?