Answer
🧪 pH Scale and Substance Classification
Statement
“Any substance below pH 7 is considered acidic, and any substance above pH 7 is considered basic or alkaline.”
✅ Answer: TRUE
What is pH?
pH is a measure of the hydrogen ion concentration in a solution. It is calculated as:
pH = -log[H⁺]The scale ranges from 0 to 14, with 7 being neutral.
pH Scale Interpretation
| pH Range | Classification | Hydrogen Ion Concentration |
|---|---|---|
| 0 – 6.9 | Acidic | High [H⁺] |
| 7 | Neutral | Equal [H⁺] and [OH⁻] |
| 7.1 – 14 | Basic (Alkaline) | Low [H⁺] |
Examples
- Acidic substances (pH < 7): Lemon juice (pH ~2), Vinegar (pH ~3), Stomach acid (pH ~1.5)
- Basic substances (pH > 7): Baking soda solution (pH ~8.3), Soapy water (pH ~10), Bleach (pH ~12–13)
Conclusion
The classification of substances based on pH is correct. Substances with:
- pH < 7 are acidic
- pH = 7 is neutral
- pH > 7 are basic or alkaline
✔ Therefore, the statement is TRUE.