Experiment 1: Acidity of Common Household Products Table 2: Acid-Base Neutraliza
ID: 887383 • Letter: E
Question
Experiment 1: Acidity of Common Household Products
Table 2: Acid-Base Neutralization for Part 1, Steps 5 & 6
Test tube 1
Test tube 2
Standard
Step 1
Add acid
Add base
Neutral
Color
Purple
Green
Purple
pH value
3
8
3.5
Table 3: Acid-Base Neutralization for Part 1, Steps 8 & 9
Test tube 1
Test tube 2
Standard
Step 1
Add base
Add acid
Neutral
Color
Light Purple
Purple
Purple
pH value
4
4
3.5
Questions
Why did the grape juice change color when an acid or base was added?
You added a base, sodium bicarbonate, to test tube 1 that contained citric acid and an acid to test tube 2 that contained base. Why did the grape juice return to its original color?
Test tube 1
Test tube 2
Standard
Step 1
Add acid
Add base
Neutral
Color
Purple
Green
Purple
pH value
3
8
3.5
Explanation / Answer
Grape juice contains tartaric acid, malic acid and citric acid. When you add acid the color changes due to dilution and/or an acid which dissocaites differentally so not givign a diffierent pH solution. Whe base is added the acid in grape juice gets neutralized and hence the color changes to more basic scale of pH.
The addition of NaHCO3 neutralized the acid present in grape juice and formed the salt of it. When again the acid is added to it, the salt breaks down to the neutral acid form again as present in the original grape juice solution. This thus returns grape juice to its original color.
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