Distilled water normally contains dissolved CO2. When preparing NaOH standard solutions, it is important to use CO2 free distilled water. How does dissolved CO2 in distilled water affect the accuracy of the determination of a NaOH solution’s concentration?
would it be too acidic?
Yes, dissolved CO2 in distilled water can make it slightly acidic, leading to an inaccurate determination of NaOH solution concentration.
When CO2 dissolves in water, it forms carbonic acid (H2CO3), which results in a decrease in the pH of the solution. This decrease in pH can interfere with the accurate determination of NaOH concentration.
During the preparation of NaOH standard solutions, the concentration is determined by titration, a process where a known concentration of NaOH solution is reacted with an acidic solution until a reaction endpoint is reached. The endpoint is typically indicated using an indicator or pH meter.
If the distilled water used in the preparation of the NaOH standard solution contains dissolved CO2, it can lower the pH of the solution, resulting in an acidic environment. This can cause the pH endpoint of the titration to shift, making it difficult to accurately determine the concentration of NaOH. Consequently, this can lead to inaccuracies in the calculated concentration of NaOH.
To avoid this issue, it is essential to use CO2-free distilled water when preparing NaOH standard solutions. CO2-free distilled water can be obtained by bubbling pure nitrogen gas or by boiling the distilled water for a few minutes to remove the dissolved CO2. This ensures that the pH of the solution remains stable during the titration, allowing for a more accurate determination of NaOH concentration.