Understanding the pH of a 2% Sodium Hydroxide Solution
Sodium hydroxide (NaOH), commonly known as lye or caustic soda, is a powerful alkaline compound frequently used in various industrial and laboratory applications. A 2% NaOH solution, which contains 20 grams of sodium hydroxide dissolved in 1 liter of water, is of significant interest due to its relatively moderate concentration compared to more concentrated forms.
The pH scale, which ranges from 0 to 14, measures the acidity or alkalinity of a solution, with values below 7 indicating acidity, 7 being neutral, and above 7 indicating alkalinity. Sodium hydroxide is a strong base, and when dissolved in water, it dissociates completely into sodium ions (Na⁺) and hydroxide ions (OH⁻). The presence of these hydroxide ions is crucial in determining the pH of the solution.
For a 2% NaOH solution, the molarity can be calculated to understand its pH more precisely. The molar mass of sodium hydroxide is approximately 40 g/mol. Therefore, a 2% solution equates to about 0.5 moles of NaOH in 1 liter of solution (20 g / 40 g/mol = 0.5 mol). To determine the pOH, we can use the formula
\[ \text{pOH} = -\log[\text{OH}^-] \]
Since the concentration of hydroxide ions is 0.5 mol/L, the pOH of the solution is
\[ \text{pOH} = -\log(0.5) \approx 0.301 \]
The pH can then be determined using the relationship between pH and pOH
\[ \text{pH} + \text{pOH} = 14 \]
By substituting our pOH value
\[ \text{pH} = 14 - 0.301 \approx 13.699 \]
Thus, the pH of a 2% NaOH solution is approximately 13.7, indicating a highly alkaline solution. This high pH level highlights the caustic nature of sodium hydroxide, which can cause severe burns and damage to tissue upon contact.
In laboratory practices, understanding the pH of a sodium hydroxide solution is vital, especially in titrations, neutralization reactions, and various chemical syntheses. Proper handling and safety measures must be observed, including wearing appropriate personal protective equipment, such as goggles and gloves, to prevent injury.
In conclusion, a 2% sodium hydroxide solution exhibits a very high pH value of approximately 13.7, reflecting its strong basic characteristics. Such solutions serve an essential role in both industrial and laboratory settings, necessitating careful handling and precise understanding of their properties.