Question

The \(\mathrm{pH}\) range if methyl red indicator is: (a) \(4.2\) to \(6.3\) (b) \(8.3\) to \(10.0\) (c) \(8.0\) to \(9.6\) (d) \(6.8\) to \(8.4\)

Short answer

The pH range for methyl red indicator is (a) 4.2 to 6.3.

Step-by-step solution

Understand the Problem

The problem provides four different \(\mathrm{pH}\) ranges (a, b, c, and d). We need to identify which of these matches the \(\mathrm{pH}\) range for the methyl red indicator.

Recall Methyl Red pH Range

Methyl red is a common indicator used in chemistry, known to change color between two pH values. The pH range for methyl red is from approximately \(4.4\) to \(6.2\).

Compare Each Option

Now, we need to compare the pH range of methyl red with each of the given options. \ \- Option (a) is \(4.2\ to\ 6.3\). \ \- Option (b) is \(8.3\ to\ 10.0\). \ \- Option (c) is \(8.0\ to\ 9.6\). \ \- Option (d) is \(6.8\ to\ 8.4\).

Identify Correct Option

Option (a) \(4.2\ to\ 6.3\) is the only range that overlaps with the methyl red range of \(4.4\ to\ 6.2\), covering the entire spectrum within the effective pH range for this indicator.

Key concepts

Acid-Base Indicators

Acid-base indicators are essential tools in chemistry for detecting the acidity or alkalinity of a solution. These indicators are typically weak acids or bases themselves that change color depending on the \(\mathrm{pH}\) of the solution they are in. Each indicator works effectively over a specific \(\mathrm{pH}\) range and is characterized by this distinct color change.

When added to a solution, acid-base indicators will exist in two different colored forms. The actual color observed in the solution will depend on whether the indicator is primarily in its acid form or base form. For instance, in an acidic solution, the indicator might be one color, while in a basic solution, it might be another color. This is due to the dissociation of the indicator molecule, which is influenced by the \(\mathrm{pH}\) of the surrounding environment.

Choosing the right acid-base indicator is crucial for achieving accurate \(\mathrm{pH}\) measurements. When the \(\mathrm{pH}\) of a solution falls within the effective range of the indicator, a clear and discernible color change occurs, providing useful visual cues for the experimenter. This is especially important in titration experiments, where the endpoint is indicated by a permanent color change in the indicator.

Methyl Red

Methyl red is a specific type of acid-base indicator commonly used in various chemistry applications. It is notable for its sharp color change from red to yellow, occurring as the \(\mathrm{pH}\) changes within its effective range. This makes it extremely useful for experiments where the \(\mathrm{pH}\) transition is expected to occur in a slightly acidic region.

The effective \(\mathrm{pH}\) range for methyl red is approximately from \(4.4\) to \(6.2\). Within this range, methyl red shifts from its acidic form, which is red, to its basic form, which is yellow. The color transition is distinct and occurs rapidly, making methyl red a preferred choice when working with acid-base titrations in this \(\mathrm{pH}\) range.

Some key characteristics of methyl red include:

• Distinct color transition from red to yellow.
• Effective in slightly acidic solutions.
• Frequently used in titrations involving weak acids and strong bases or vice versa.

While methyl red is highly effective within its range, it is important to choose a different indicator if the expected \(\mathrm{pH}\) transition falls outside of \(4.4\) to \(6.2\), to ensure accuracy and precision in your experiment.

pH Range

The \(\mathrm{pH}\) range of a solution determines its acidity or basicity and is a crucial parameter in various chemical processes. The \(\mathrm{pH}\) scale typically runs from \(0\) to \(14\), with \(7\) being neutral. Values below \(7\) indicate acidic solutions, while values above \(7\) denote basic or alkaline solutions.

In the context of acid-base indicators like methyl red, understanding the \(\mathrm{pH}\) range is vital for predicting the indicator's performance. Methyl red, for instance, operates effectively between \(4.4\) and \(6.2\), which makes it suitable for slightly acidic environments. This range is critical for choosing when to use this indicator in experiments such as titrations.

The selection of the correct \(\mathrm{pH}\) range in any chemical process ensures accurate monitoring and control, particularly in processes like:

• Neutralizations in titrations.
• Quality control in laboratories.
• Environmental testing and monitoring.

Careful consideration and understanding of the \(\mathrm{pH}\) ranges help chemists and scientists pinpoint the right conditions under which an indicator will offer reliable and visible results, enhancing the validity and success of their experiments.