What would be the colour change when we add phenolphthalein to glucose solution?
The Correct Answer and Explanation is:
When phenolphthalein is added to a glucose solution, there is generally no significant color change observed. This is because glucose is a neutral substance, and phenolphthalein, which is an indicator, typically changes color in response to pH changes, particularly in basic (alkaline) environments.
Phenolphthalein is colorless in acidic and neutral conditions but turns pink or magenta in basic (alkaline) conditions. It undergoes a structural change when exposed to hydroxide ions (OH-) in a basic solution, causing the color change.
Glucose itself does not significantly alter the pH of a solution, as it is neither strongly acidic nor basic. When dissolved in water, glucose forms a neutral solution (pH 7). Therefore, when phenolphthalein is added to a glucose solution, the solution would remain colorless, indicating a neutral pH.
However, if the glucose solution is mixed with a strong base, such as sodium hydroxide (NaOH), the pH of the solution would increase, and the phenolphthalein would turn pink, signifying an alkaline environment. But in the case of just glucose and phenolphthalein alone, there is no significant color change since the solution remains neutral.
This behavior is an example of how the function of pH indicators, like phenolphthalein, depends largely on the pH of the solution they are added to, and not on the substance (in this case glucose) unless it alters the pH.
