If a solution of NaOH is left exposed to room air, what will happen to its pH? What chemical
equilibrium is responsible for this effect?
NaOH absorbs CO2 from the atmosphere and pH decreases.
Do you know what chemical equilibrium is responsible for this effect?
NaOH + CO2 ==> NaHCO3 or you can write
CO2 + H2O ==> H2CO3, then
H2CO3 + NaOH ==> NaHCO3 + H2O
When a solution of NaOH (sodium hydroxide) is left exposed to room air, it will react with the carbon dioxide (CO2) present in the air. This reaction leads to the formation of sodium carbonate (Na2CO3) through a chemical equilibrium process known as the carbonation of sodium hydroxide.
The reaction can be expressed as:
2 NaOH + CO2 -> Na2CO3 + H2O
As a result of this reaction, the pH of the NaOH solution will increase. This means that the solution will become more alkaline or basic.
To understand why the pH increases, it is important to grasp the concept of pH. pH is a measure of the acidity or alkalinity of a solution. It is determined by the concentration of hydrogen ions (H+) present in the solution.
Sodium hydroxide is a strong base that dissociates completely in water, resulting in the production of hydroxide ions (OH-). These hydroxide ions react with hydrogen ions from water (H2O) to form water molecules (H2O). Therefore, when the concentration of hydroxide ions increases due to the reaction with carbon dioxide, the concentration of available hydrogen ions decreases. This reduction in hydrogen ion concentration leads to an increase in pH, making the solution more basic.
In summary, when a solution of NaOH is exposed to room air, it reacts with carbon dioxide from the air, leading to the formation of sodium carbonate and an increase in pH.