Question

What colors does the pH indicator phenol red turn to at certain pHs?

Answer 1

Phenol red is a pH indicator that changes color based on the pH level: yellow in acidic solutions, red in neutral, and pink to purple in basic solutions. These colors indicate the approximate pH of the solution within a range, rather than at a precise pH value.

Step-by-step explanation:

pH Indicator Color Change

The pH indicator phenol red exhibits a color change depending on the pH level of the solution it is in. In acidic environments, phenol red is yellow, shifting to red in neutral conditions (around pH 7), and then turning pink to purple in basic or alkaline solutions (pH above 7). It is important to note that pH indicators, including phenol red, are usually weak acids or bases. The color transition does not occur abruptly at a single pH value but over a range of pH values.

Choosing the appropriate indicator depends on the specific pH range in which the indicator exhibits the color change. For example, phenolphthalein is another pH indicator, which is colorless in acidic solutions and turns pink in basic solutions, with a transition around pH 8.3. The color change happens over a range of pH values, allowing for estimation of the pH level within that range.

Answer 2

Phenol red turns yellow below a pH of 6.8, red from pH 6.8 to 8.1, and deep red to purple above pH 8.1, allowing for the estimation of a solution's pH level.

Step-by-step explanation:

The question pertains to the color changes that the pH indicator phenol red exhibits at different pH levels. Phenol red is a pH indicator commonly used in laboratories to gauge the acidity or alkalinity of a solution, undergoing a distinct and observable color shift.

Phenol red exhibits a yellow color at a pH below 6.8, indicating an acidic environment. At a pH ranging from 6.8 to 8.1, phenol red turns red, which signifies a neutral to slightly alkaline condition. If the pH rises above 8.1, the indicator turns a deep red to purple, which is indicative of a more highly alkaline solution.

Therefore, by observing the color presented by phenol red in a solution, one can determine the general pH range of that solution, making phenol red a useful tool for quick pH estimation in various chemical and biological applications.