The Impact of Adding Sodium Hydroxide to Water: A pH Analysis

The addition of sodium hydroxide (NaOH) to water is a commonly studied chemical reaction in both academic and industrial settings. This reaction significantly alters the pH of the solution, making it a relevant topic for students, chemists, and environmental scientists. This article will provide a detailed explanation of how the pH of water changes when a small amount of sodium hydroxide is added.

Understanding the Reaction

Sodium hydroxide, a strong base, undergoes a complete dissociation in water, forming sodium ions (Na ) and hydroxide ions (OH-).

When 0.01 mole of sodium hydroxide is added to 10 liters of water, the dissociation of NaOH is as follows:

NaOH xrightarrow{} Na^ OH^-

Calculating the pH Change

To calculate the pH change, the following steps need to be followed:

Step 1: Calculate the Concentration of NaOH

First, we need to calculate the concentration of NaOH. The molarity (M) of a solution is defined as the number of moles of solute per liter of solution:

Molarity (M) frac{0.01 , text{moles}}{10 , text{liters}} 0.001 , text{M}

Step 2: Determine the Effect of NaOH on pH

Since NaOH is a strong base, it dissociates completely into sodium ions (Na ) and hydroxide ions (OH-). Therefore, the concentration of OH- ions is also 0.001 M.

Given this, the concentration of hydroxide ions is:

Concentration of OH- 0.001 M

Step 3: Calculate the pOH

The pOH of a solution is defined as the negative logarithm (base 10) of the hydroxide ion concentration:

pOH -log[OH-]

Substituting the concentration of OH- ions:

pOH -log(0.001) 3

Step 4: Convert pOH to pH

The relationship between pH and pOH is given by:

pH pOH 14

Therefore, the pH can be calculated as follows:

pH 14 - pOH 14 - 3 11

Conclusion

The addition of 0.01 moles of sodium hydroxide to 10 liters of water will significantly increase the pH of the solution from its neutral value of 7 to approximately 11. This increase is due to the high concentration of hydroxide ions introduced by the strong base NaOH.

This understanding of how the pH of water changes when sodium hydroxide is added is crucial for a wide range of applications, including environmental monitoring, industrial processes, and academic research.

Keywords: pH change, sodium hydroxide, water chemistry