Question

Paheli was carrying out a Neutralisation reaction in her school laboratory.
She took 10 ml of an acid and added the indicator Phenolphthalein to it. What will she observe and why?
Next, she started adding some base dropwise to it. What will her observation be? Support your answer with a valid reason.
How will Paheli be capable of reversing this colour change?

Answer 1

Answer:

When phenolphthalein is added to the base the colour of the solution intensifies and if it is added to an acidic solution the colour will fade away and become colourless. Complete step by step answer: Phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations.

Explanation:

Answer 2

Initially, when Paheli adds acid to Phenolphthalein, there will be no change in color. Later, when she adds some base to it the color of the solution will change to pink. She can reverse this color change by adding a few more drops of the base to the solution drop by drop.

• Phenolphthalein is an acid-base indicator that does not change color when added to an acid. So when Paheli adds acid to the indicator she does not observe any color change.
• Phenolphthalein gives pink color when added to the base. This is the reason why she will observe the change of color of the mixture to pink after adding a few drops of the base to the solution.
• She can easily reverse the color change by adding a few more drops of the base to the solution as by doing so the solution will be neutralized to give water and salt, and Phenolphthalein remains colorless for a solution of pH level 7 (that of the water) or less than that.

So, these are all the color changes she will observe and can reverse the color change by continuing to add a few more drops of the base to the solution.