The color red in pH indicators typically indicates a strong acid environment, corresponding to a pH of approximately 3 or lower.
Here's a more detailed breakdown:
Universal indicators are mixtures of several different indicators that exhibit a range of colors across the pH spectrum. The color observed depends on the hydrogen ion concentration in the solution.
| pH Range | Description | Color |
|---|---|---|
| ≤ 3 | Strong Acid | Red |
| 4–6 | Weak Acid | Orange/Yellow |
| 7 | Neutral | Green |
| 8–10 | Weak Alkali | Blue |
| ≥ 11 | Strong Alkali | Violet/Purple |
Therefore, when using a universal indicator, a solution turning red suggests a highly acidic condition. The exact pH corresponding to red can vary slightly depending on the specific indicator mix, but it generally falls at or below pH 3.
