Observe the statements. I. Phenolphthalein is a colourless solution II. Phenolphthalein turns pink in basic solution III. Phenolphthalein turns red in acidic solution IV. Phenolphthalein remains colourless in acidic solution Choose the correct option a. I &II are correct b. I & III are correct c. I ,II & IV are correct d. All the statements are correct

c.I ,II & IV are correct

Explanation:

Phenolphthalein is an indicator. An indicator is an organic dye whose solution changes colour as the concentration of hydrogen ions in solution changes.

Hence a typical indicator exhibits different colours at different pH ranges. The colour of an indicator in an acid, a base and at end point always differs.

Phenolphthalein  is a colourless solution which has a pink colour in an alkaline medium and colourless in an acidic medium.

sure what is it? ^w^

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.