A pH of 12 indicates a(n):
A. weak acid
B. weak base
C. strong acid
D. strong base
The Correct Answer and Explanation is:
The correct answer is:
D. strong base
A pH of 12 indicates a strong base. The pH scale ranges from 0 to 14 and measures the concentration of hydrogen ions (H⁺) in a solution. It is logarithmic, meaning each unit change represents a tenfold difference in H⁺ concentration. A neutral pH, such as pure water, is 7, where the concentration of H⁺ ions is equal to the concentration of hydroxide ions (OH⁻).
Understanding pH Levels:
- Acids have a pH less than 7. The lower the pH, the more acidic the substance. A strong acid, such as hydrochloric acid (HCl), typically has a pH closer to 0-3. A weak acid, like acetic acid (vinegar), might have a pH closer to 4-6.
- Bases have a pH greater than 7. The higher the pH, the more basic (alkaline) the substance. A strong base, such as sodium hydroxide (NaOH), has a pH closer to 12-14. A weak base, like ammonia, usually has a pH around 8-10.
A pH of 12 suggests that the concentration of OH⁻ ions is very high compared to H⁺ ions, making the solution strongly basic. Strong bases dissociate completely in water, meaning they release a significant amount of OH⁻ ions, reducing the presence of H⁺ ions significantly. This explains why the pH is high.
Strong Bases vs. Weak Bases:
A strong base (pH 11-14) dissociates fully, leading to high alkalinity, which makes it highly reactive. Examples include NaOH and potassium hydroxide (KOH). These are used in cleaning products due to their ability to neutralize acids and break down organic material.
On the other hand, a weak base (pH 8-10) only partially dissociates in water, resulting in fewer OH⁻ ions in the solution. These include compounds like ammonia (NH₃).
Therefore, a solution with a pH of 12 is classified as a strong base, indicating its high alkalinity and strong reactivity in neutralizing acids.