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Indicator Range Part B

Indicator
Starting pH Level
Starting Color
pH Level
Color
Effectiveness
Red Cabbage
6.76 (with HCl)
Light purple
tinged with pink
3.00
Cherry Red
Most effective, widest range
covers acids as well as bases
 
 
 
4.00
Magenta
 
 
 
 
4.94
 
 
 
 
 
6.20
Royal Purple
 
 
7.00 (with NaOH)
 
8.40
Turquoise
 
 
 
 
9.40
Blue-Green
 
 
 
 
10.10
Dark Green
 
 
 
 
11.40
 
 
 
 
 
12.00
Green
 
 
 
 
12.23
Green-Yellow
 
 
 
 
13.00
Yellow
 
Red Chard
7.03
Dark Forest Green
No change
 
Not effective
Carrots
6.04
Orange
No change
 
Not effective
Grapes
4.23 (with NaOH)
Clear tan
8.00
Amber
Small range, only detects
bases, subtle color changes
 
 
 
10.00
Darker amber
 
Cranberries
2.70 (with NaOH)
Deep, dark red (crimson)
4.80
Darker Red
Larger range than grapes,
but still small
 
 
 
5.40
Burgandy
 
 
 
 
7.30
Deep Charcoal
 
 
 
 
7.30+
Black
 
Blueberries
4.03 (with NaOH)
Purplish pink
7.00
Olive Green
Slightly larger range than
grapes, also has subtle
color changes
 
 
 
7.00+
Darker Olive
 

           Red chard and carrots did not change colors at all, probably because they do not have the necessary antocyanines. I discarded these 2 indicators because they are completely ineffective and useless for the purposes of the experiment.

           A trend I observed is the fact grapes, cranberries, and blueberries are all acidic by nature, so they can only change colors in solutions more basic than they are. Following this observed trend, red cabbage has the widest range, covering both acids and bases, because it is originally neutral.



Test Results Part C

 
pH level (using pH meter)
Color with:
 
 
 
 
 
Substance
 
Red Cabbage
Grapes
Cranberries
Blueberries
Estimated pH
% Error
White vinegar
2.80
Bubble-gum pink
No change
No change
No change
3.50
25%
Lemon juice
2.50
Bubble-gum pink
No change
No change
No change
3.50
40%
Orange juice
4.60
Light magenta
No change
No change
No change
4.50
2%
Grapefruit juice
2.80
Buble-gum pink
No change
No change
No change
3.50
25%
Egg whites
8.60
Green-blue
Amber
Burgundy
Olive green
8.00
7%
Baking soda
7.86
Gray-blue
Darker tan
Charcoal
Light olive green
7.50
5%
 
*Make sure the
baking soda
concentration
is the same
for each
indicator
 
Bleach
9.50
Pale yellow
Lemonade yellow
Highlighter yellow
Cream soda colored
Undecided
N/A
Windex
9.40
Bright green
Gray-green
Black
Olive green
12.00
28%
Sprite
3.20
Light pink
No change
No change
No change
5.00
56%


           It was difficult determining the pH level of a lot of the substances because the colors the indicator and the substance produced did not match the color scale from Part B of the procedure. For example, bubble-gum pink did not appear on the color scale from Part B. However, though bubble-gum pink was not on the original color scale, all the substances that turned bubble-gum pink (vinegar, lemon, and grapefruit) were very close in pH, only varying by 0.30.

           It was especially hard to determine the pH for acidic substances because only red cabbage could detect acids. To solve this problem, several more indicators able to change color in acid could be used; this way the estimated pH wouldn't be based on only one indicator.

           Some colors that didn't appear on the color scale, resulted from reactions with the chemicals in the substance and not from the pH level. For instance, grape juice reacted with Windex to form a gray-green color, which is very different from the expected amber color. Bleach, too, reacted in unexpected ways with all of the indicators, making it impossible to determine its the pH level.

           Another improvement to the procedure would be to conduct more than one trial for Part B of the procedure. That way, a more accurate color scale could be determined to provide more accurate results.


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