What is the Ph of calcium hydroxide?
**Core Concept:** The question is asking about the pH (acidity or alkalinity) of calcium hydroxide, which is a compound used in dental and medical applications due to its bactericidal, anti-inflammatory, and sealing properties.
Calcium hydroxide is mainly composed of calcium ions (Ca2+) and hydroxide ions (OH-). In aqueous solutions, calcium hydroxide dissociates into its constituent ions:
Calcium hydroxide (Ca(OH)2) -> Calcium ion (Ca2+) + Hydroxide ion (OH-)
**Why the Correct Answer is Right:** Calcium hydroxide has a high affinity for water molecules, which enhances its solubility in water. When calcium hydroxide dissociates into its constituent ions, it results in a solution with a high concentration of hydroxide ions (OH-).
**Why Each Wrong Option is Incorrect:**
A. 14 (neutral pH) - This option is incorrect because calcium hydroxide has a higher concentration of hydroxide ions (OH-) compared to a neutral solution (pH 7). A solution with a higher concentration of hydroxide ions is alkaline, not neutral.
B. 11 (slightly acidic pH) - This option is incorrect due to the high concentration of hydroxide ions (OH-) in calcium hydroxide solutions. As mentioned earlier, calcium hydroxide is alkaline, not acidic.
C. 9 (alkaline pH) - This option is incorrect due to the high concentration of hydroxide ions (OH-) in calcium hydroxide solutions. As mentioned earlier, calcium hydroxide is alkaline, not neutral.
D. 7 (neutral pH) - This option is incorrect as calcium hydroxide has a higher concentration of hydroxide ions (OH-) compared to a neutral solution (pH 7). A solution with a higher concentration of hydroxide ions (OH-) is alkaline, not neutral.
**Clinical Pearls:**
1. Calcium hydroxide is commonly used in dental pulp therapy to inhibit bacterial growth due to its alkalinity (high pH).
2. Calcium hydroxide paste is used in endodontics for root canal therapy and as an intracanal medication due to its bactericidal and anti-inflammatory properties.
3. The pH scale ranges from 0 to 14, with 7 being neutral. Solutions with a pH lower than 7 are acidic, and solutions with a pH greater than 7 are alkaline (or basic).