Calcium hydroxide, also known as slaked lime or hydrated lime, is a chemical compound with the formula Ca(OH)2. It is a white powder or crystals that is used in a variety of industrial and commercial applications, such as in the production of cement, glass, and paper. Calcium hydroxide is also used as a water treatment agent and as a fertilizer. As a base, calcium hydroxide has a pH of 12.4, making it a strong base. It is also a caustic substance, which means that it can cause burns or irritation to the skin and eyes.
The Complex Nature of Calcium Hydroxide
Understanding pH and Basicity
The strength of a base is determined by its ability to donate hydroxide ions (OH-) to a solution. This ability is measured by the pH scale, which ranges from 0 to 14. A lower pH indicates a higher concentration of hydrogen ions (H+), making the solution more acidic. Conversely, a higher pH indicates a higher concentration of OH- ions, making the solution more basic.
Calcium Hydroxide: A Moderate Base
Calcium hydroxide, Ca(OH)2, is a moderately strong base with a pH of about 12.5 in a saturated solution. This means it readily dissociates in water to release OH- ions:
Ca(OH)2(s) → Ca2+(aq) + 2OH-(aq)
Factors Influencing Basicity
Several factors influence the basicity of calcium hydroxide:
- Solubility: Ca(OH)2 has a relatively low solubility in water. This limits the number of OH- ions that can be released into solution, reducing its basicity.
- Temperature: Basicity increases with temperature because higher temperatures favor the dissociation of Ca(OH)2 into ions.
- Presence of Other Ions: Ions such as carbonate or sulfate can compete with calcium for hydroxide ions, reducing the basicity of the solution.
Comparison with Other Bases
- Strong Bases: Strong bases, such as sodium hydroxide (NaOH) and potassium hydroxide (KOH), completely dissociate in water, releasing a maximum number of OH- ions. They have pH values close to 14.
- Weak Bases: Weak bases, such as ammonia (NH3) and acetic acid (CH3COOH), only partially dissociate in water, releasing a smaller number of OH- ions. They have pH values below 12.
Table: Basicity of Common Substances
| Substance | pH |
|---|---|
| Strong Base (e.g., NaOH) | 14 |
| Moderate Base (e.g., Ca(OH)2) | 12.5 |
| Weak Base (e.g., NH3) | 11 |
| Neutral (e.g., Pure Water) | 7 |
| Acid (e.g., HCl) | 1 |
Question: Does calcium hydroxide qualify as a strong base?
Answer: Yes, calcium hydroxide is a strong base. It dissociates completely in water to produce hydroxide ions (OH-), which is a strong base.
Question: What is the pH of a saturated calcium hydroxide solution?
Answer: The pH of a saturated calcium hydroxide solution is approximately 12.4. This indicates that it is a highly alkaline solution due to the presence of a high concentration of hydroxide ions.
Question: How does calcium hydroxide compare to sodium hydroxide in terms of strength?
Answer: Calcium hydroxide is a slightly weaker base than sodium hydroxide. This is because calcium ions (Ca2+) have a larger ionic radius than sodium ions (Na+), which results in weaker electrostatic attraction between the calcium ions and the hydroxide ions.
Well, there you have it. Calcium hydroxide is a strong base, but it’s not the strongest one out there. It’s still a powerful substance, though, so be careful when you’re working with it. Thanks for reading, and be sure to visit again later for more chemistry fun!