what is it important to keep the NaOH solution covered at all times?

How will the molarity of the NaOH solution be affected by its continued exposure to the atmosphere?

The pale pink color of the titration solution at the end point will fade to colorless after several minutes when exposed to the atmosphere. Account for this color change.

Think about what carbon dioxide forms when it dissolves in water.

1. It is important to keep the NaOH solution covered at all times to prevent the absorption of moisture and carbon dioxide from the air. NaOH is hygroscopic, meaning that it readily absorbs water from the surrounding environment. Exposure to moisture can cause the concentration of the solution to change, affecting the accuracy of any subsequent measurements or reactions.

2. The continued exposure of the NaOH solution to the atmosphere will result in the absorption of carbon dioxide. Carbon dioxide reacts with NaOH to form sodium carbonate (Na2CO3) through a process known as carbonation. This reaction reduces the concentration of NaOH in the solution, leading to a decrease in its molarity.

3. The pale pink color observed at the end point of the titration is due to a pH indicator called phenolphthalein. Phenolphthalein is a weak acid that is colorless in acidic solutions and pink in alkaline solutions. However, when the titration solution is exposed to the atmosphere, carbon dioxide from the air dissolves into the solution and forms carbonic acid (H2CO3). Carbonic acid is a weak acid that neutralizes the NaOH, resulting in a decrease in the pH of the solution. As the pH decreases, phenolphthalein loses its alkaline properties and turns colorless. Therefore, the pale pink color of the titration solution fades to colorless after several minutes when exposed to the atmosphere due to the formation of carbonic acid.

It is important to keep the NaOH (sodium hydroxide) solution covered at all times for a few reasons.

Firstly, NaOH is hygroscopic, meaning it readily absorbs moisture from the atmosphere. If the solution is left uncovered, water vapor in the air can be absorbed by the NaOH, leading to an increase in the concentration of the solution. This increase in concentration can affect the accuracy of any experiments or reactions that require a specific molarity of NaOH.

Secondly, NaOH is a corrosive substance, and it can cause serious burns and irritations upon contact with the skin or eyes. By keeping the solution covered, you reduce the risk of splashing or accidental exposure to the solution.

Continued exposure of the NaOH solution to the atmosphere can affect its molarity. As mentioned earlier, NaOH is hygroscopic, which means it absorbs moisture from the air. If the solution is left uncovered, it will gradually absorb water vapor from the surroundings, leading to an increase in the concentration of the solution. This increase in concentration will cause the molarity of the NaOH solution to increase.

When performing a titration using NaOH, a phenolphthalein indicator is often used. Phenolphthalein is a pH indicator that is colorless in acidic solutions and turns pink as the solution becomes alkaline. At the endpoint of the titration, when all the acid has reacted with the base, the solution will turn pale pink indicating that the reaction is complete.

However, when the titration solution is exposed to the atmosphere for several minutes after reaching the endpoint, the pale pink color can fade and become colorless. This color change occurs because carbon dioxide (CO2) from the atmosphere reacts with the NaOH to form sodium carbonate (Na2CO3), which is a white solid. The formation of sodium carbonate changes the pH of the solution, causing the phenolphthalein indicator to become colorless.

In summary, it is important to keep the NaOH solution covered at all times to prevent moisture absorption, maintain the desired molarity, and reduce the risk of accidental exposure. The color change of the titration solution from pale pink to colorless is due to the reaction of CO2 from the atmosphere with the NaOH, forming sodium carbonate and changing the pH of the solution.