Question

The acid-base indicator methyl orange changes color from \(\mathrm{pH} 3.2\) to \(\mathrm{pH}\) 4.4. It appears red in strongly acidic solutions and yellow in basic solutions. Predict the color of the indicator in a solution having a \(\mathrm{pH}\) of 3.8.

Short answer

The solution with pH 3.8 will appear orange.

Step-by-step solution

Understand the Color Change Range

Methyl orange changes color based on the pH level of the solution. Below pH 3.2, it appears red, and above pH 4.4, it becomes yellow. Between these values, the color transitions from red to yellow, showing mixtures of these colors such as orange in between.

Locate the pH within the Transition Range

The solution has a pH of 3.8. This value is between the pH range of 3.2 and 4.4, where the transition of colors from red to yellow happens.

Predict the Intermediate Color

As the pH of 3.8 falls right in the middle of the transition range, the expected color is likely to be an orange hue, which is a mix between red and yellow.

Key concepts

Methyl Orange

Methyl orange is an acid-base indicator commonly used in titrations. It helps to determine the endpoint by changing color when the acidity or basicity of a solution changes. This color change is a result of structural changes in the methyl orange molecule that occur in response to the concentration of hydrogen ions, or simply put, changes in pH levels.

Methyl orange is particularly known for its distinctive color change from red in acidic environments to yellow in alkaline conditions. In the acidic range, particularly below a pH of 3.2, methyl orange appears distinctly red. As the pH moves beyond 4.4 into more basic territories, the indicator shifts to yellow. In solutions between these pH levels, the color transition becomes a useful tool for observing pH changes. By understanding how methyl orange behaves, one can make quick determinations about the acidity or basicity of a given solution.

pH Scale

The pH scale is a logarithmic scale used to specify the acidity or basicity of aqueous solutions. It ranges from 0 to 14, where lower numbers are more acidic, and higher numbers are more basic. A pH of 7 is considered neutral, characteristic of pure water.

While the scale provides an easy way to assess the hydrogen ion concentration in a solution, it's not just limited to the theoretical understanding. Indicators like methyl orange leverage this scale to provide visual cues of chemical environments. For instance, knowing the pH at which an indicator changes color allows scientists and students alike to determine the pH of a solution quickly and effectively.

• pH below 7: Acidic solutions
• pH of 7: Neutral solutions
• pH above 7: Basic solutions

Utilizing the pH scale, practical applications such as titrations and environmental testing become more accessible and reliable.

Color Change in Solutions

Color change in solutions is a fascinating phenomenon that occurs when the properties of a solution alter, often due to chemical reactions or change in pH.

Indicators like methyl orange are used to monitor these changes visually. As the pH of a solution moves through its designated range, the indicator undergoes a chemical modification that results in a different color. For methyl orange, the transition happens between pH 3.2 to 4.4, bridging the spectrum from red to yellow.

In the pH transition area, various shades are observed; for example, a pH of 3.8 would show an orange hue. This intermediate color suggests a midpoint balance in the transition range, showing the blend of acidic red and alkaline yellow colors. Understanding such changes is integral to processes in analytical chemistry, where precise color changes can infer detailed information about the solution’s composition and behavior.