## **Core Concept**
The pH of a solution is a measure of its acidity or alkalinity, which is crucial in various medical and dental applications, including the use of sodium hypochlorite (NaOCl) as a disinfectant and root canal irrigant. Sodium hypochlorite solutions are commonly used for their antimicrobial properties. The pH of a NaOCl solution depends on its concentration and the presence of other chemicals.

## **Why the Correct Answer is Right**
Sodium hypochlorite (NaOCl) solutions are alkaline in nature. When dissolved in water, NaOCl completely dissociates into sodium ions (Na+) and hypochlorite ions (OCl-). The hypochlorite ion can react with water to form hydroxide ions (OH-), which increase the pH of the solution. Typically, commercial NaOCl solutions, such as bleach, have a pH in the alkaline range due to the formation of these hydroxide ions. A pH of **12** is commonly cited for concentrated solutions, reflecting their strong alkaline nature.

## **Why Each Wrong Option is Incorrect**
- **Option A:** A pH of 7 is neutral, which does not reflect the alkaline nature of NaOCl solutions.
- **Option B:** A pH of 4 suggests an acidic environment, which is incorrect for NaOCl solutions as they are known to be alkaline.
- **Option C:** Although closer, a pH of 10 is still not as alkaline as what is typically measured for NaOCl solutions.

## **Clinical Pearl / High-Yield Fact**
It's essential to remember that the pH of NaOCl solutions can affect their stability and efficacy as well as the tissues they come into contact with. For instance, in dental procedures, the alkaline pH of NaOCl can help dissolve organic matter but may also potentially damage tissues if not used properly.

## **Correct Answer:** D. 12.