pH of 0.1 M Sodium Bicarbonate Solution
Introduction
Sodium bicarbonate, also known as baking soda, is a widely used chemical compound with various applications in food, pharmaceutical, and medical industries. In laboratory settings, sodium bicarbonate solutions are commonly used as buffers to maintain a stable pH. In this article, we will discuss the pH of a 0.1 M sodium bicarbonate solution.
pH of Sodium Bicarbonate Solution
The pH of a sodium bicarbonate solution depends on the concentration of the solution and the pKa value of the bicarbonate ion (HCO3-). The pKa value of HCO3- is approximately 10.33. This means that at a concentration of 0.1 M, the sodium bicarbonate solution will have a pH close to the pKa value.
Calculation of pH
To calculate the pH of a 0.1 M sodium bicarbonate solution, we can use the Henderson-Hasselbalch equation:
pH = pKa + log10([Base]/[Acid])
where [Base] is the concentration of the base (sodium bicarbonate) and [Acid] is the concentration of the acid (carbonic acid).
Assuming a complete dissociation of sodium bicarbonate (NaHCO3) into sodium ions (Na+) and bicarbonate ions (HCO3-), the concentration of HCO3- is equal to the concentration of the sodium bicarbonate solution, which is 0.1 M.
The concentration of carbonic acid (H2CO3) can be calculated using the equilibrium constant expression:
K = [HCO3-][H+]/[H2CO3]
where K is the equilibrium constant, which is approximately 4.30 x 10^(-7) at room temperature.
Rearranging the equation to solve for [H2CO3], we get:
[H2CO3] = K * [HCO3-]/[H+]
Substituting the values, we get:
[H2CO3] = 4.30 x 10^(-7) * 0.1 M / [H+]
Using the Henderson-Hasselbalch equation, we can calculate the pH of the solution:
pH = pKa + log10([HCO3-]/[H2CO3]) pH = 10.33 + log10(0.1 M / [H2CO3])
Solving for pH, we get:
pH ≈ 8.34
Conclusion
The pH of a 0.1 M sodium bicarbonate solution is approximately 8.34, which is slightly basic. This is expected, given the pKa value of the bicarbonate ion and the concentration of the solution. The calculated pH value can be used as a reference for laboratory applications, such as buffering solutions, biochemical reactions, and pharmaceutical manufacturing.
Note: The calculated pH value is an approximation and may vary depending on the specific conditions of the solution, such as temperature and ionic strength.
