Seven in the middle
Below 7 is acidic, above 7 is basic, and 7 is neutral.
A pH of 10
A liquid is tested with universal indicator. The pH comes out as 10.
What kind of solution is it?
What this lesson covers
The idea
A neutral solution has pH 7, an acidic solution has pH less than 7, and as pH rises from 7 to 14 the OH– ion concentration, that is the strength of the alkali, increases.
A pH of 10
A liquid is tested with universal indicator. The pH comes out as 10.
What kind of solution is it?
- Basic (alkaline)
- Acidic
- Neutral
Sort the pH values
Put each pH into the right box.
Now look at a base. Slide to more OH⁻ ions and watch the pH.
7 is the middle
A neutral solution has pH 7. An acidic solution has a pH less than 7. As the pH rises from 7 to 14, the OH⁻ ion concentration increases: the alkali gets stronger.
pH paper (paper with universal indicator) is generally used to measure pH.
- pH | Solution | Ions
- less than 7 | acidic | more H₃O⁺
- 7 | neutral | balanced
- 7 to 14, rising | basic, stronger and stronger | more and more OH⁻
Notes
A neutral solution has pH 7, an acidic solution has pH less than 7, and as pH rises from 7 to 14 the OH⁻ ion concentration, that is the strength of the alkali, increases.
Check yourself
What is the pH of a neutral solution?
A solution has pH 4. It is …
Which is the stronger alkali: pH 9 or pH 13?
The pH of a solution rises from 8 to 12. The OH⁻ ion concentration …
- 0. 0 is the very acidic end.
- 7 — correct. Yes!
- 14. 14 is the very alkaline end.
- neutral. Neutral is exactly 7.
- basic. Bases have a pH above 7.
- acidic — correct. Yes! 4 is less than 7.
- pH 13 — correct. Yes! The higher the pH above 7, the more OH⁻ ions.
- pH 9. pH 13 has more OH⁻ ions, so it is stronger.
- They are the same. They are different. A higher pH means more OH⁻.
- decreases. In an alkali, a higher pH means more OH⁻.
- increases — correct. Yes! It becomes a stronger alkali.
- stays the same. It changes as the pH changes.