An organic compound that changes from one color to another at a certain pH is called:

An organic compound that changes from one color to another at a certain pH is called:

• A. Test solution
• B. Standard solution
• C. Buffer
• D. Indicator

Answer: (D)

A substance that changes color with pH is called an indicator. Indicators are organic dyes that exist in different forms depending on the acidity or basicity of their environment, and these forms have different colors. When the pH changes, the equilibrium between the acid and base forms shifts, producing a visible color change. This property makes indicators useful for signaling pH levels or marking the endpoint in a titration. The other terms don’t describe a color-changing compound: a test solution is any solution used to perform a test; a standard solution has a precisely known concentration; a buffer resists pH changes by neutralizing added acids or bases. Hence, the color-changing organic compound is an indicator.

A substance that changes color with pH is called an indicator. Indicators are organic dyes that exist in different forms depending on the acidity or basicity of their environment, and these forms have different colors. When the pH changes, the equilibrium between the acid and base forms shifts, producing a visible color change. This property makes indicators useful for signaling pH levels or marking the endpoint in a titration. The other terms don’t describe a color-changing compound: a test solution is any solution used to perform a test; a standard solution has a precisely known concentration; a buffer resists pH changes by neutralizing added acids or bases. Hence, the color-changing organic compound is an indicator.