Understanding the pH of a 0.1 M NaOH Solution

When dealing with aqueous solutions, the pH is a crucial measure of acidity or basicity. In this article, we will explore how to calculate the pH of a 0.1 M NaOH solution step by step. Understanding this calculation is important for various applications in chemistry and environmental science.

Components of the NaOH Solution

NaOH is a strong base, meaning it dissociates completely in water. The chemical equation for this process is: NaOH → Na? OH?

Therefore, in a 0.1 M NaOH solution, the concentration of hydroxide ions (OH?) is also 0.1 M. This is a key fact that simplifies the calculation of pH.

Calculation of pOH

The pOH is a measure of the concentration of hydroxide ions in a solution. It is calculated using the formula:

pOH -log[OH?]

Substituting the concentration of OH?:

pOH -log(0.1) 1

Conversion of pOH to pH

The relationship between pH and pOH in pure water at 25°C is given by:

pH pOH 14

Where the value of 14 is derived from the ion product of water, Kw, which is a temperature-dependent constant. The value of Kw is approximately 10?1? at 25°C.

Given that the pOH is 1, the pH can be calculated as:

pH 14 - pOH 14 - 1 13

Therefore, the pH of a 0.1 M NaOH solution is 13.

Factors Influencing pH

It is important to note that the pH equation is temperature-dependent. While the value of Kw changes with temperature, one common assumption is to use the value at 25°C where pure water has a pH of 7.

At higher temperatures, the equilibrium shifts towards the dissociation of water, leading to an increase in hydrogen ion concentration (H?) and a decrease in pH. However, for most practical purposes, the temperature is often assumed to be 25°C to simplify calculations.

Conclusion and Applications

Understanding the pH of a 0.1 M NaOH solution is crucial in many fields, including environmental science, pharmaceuticals, and industrial chemistry. By grasping the principles of pH and pOH, scientists can better understand and control the chemical reactions and environments in which these solutions operate.

Key Takeaways:

NaOH is a strong base, which fully dissociates in water, making the concentration of OH? ions 0.1 M for a 0.1 M NaOH solution. The formula for calculating pOH is: pOH -log[OH?]. The relationship between pH and pOH in pure water at 25°C is pH pOH 14. The pH of a 0.1 M NaOH solution is 13. The pH is temperature-dependent, but at 25°C, the value of Kw is 10?1?.

By following these steps and understanding these principles, chemists and researchers can ensure accurate and reliable measurements in their work.