Which statement correctly describes the color behavior of phenolphthalein and methyl orange?

Which statement correctly describes the color behavior of phenolphthalein and methyl orange?

• A. Methyl orange turns red in basic solution and yellow in acid.
• B. Both indicators change color at the same pH.
• C. Phenolphthalein turns blue in acid.
• D. Phenolphthalein is colorless below ~8.2 and pink above.

Answer: (D)

Indicators reveal pH by changing color within specific ranges. Phenolphthalein stays colorless in acidic solutions and remains colorless until about pH 8.2, then turns pink in basic solutions as pH rises toward about 10. Methyl orange is red in strongly acidic conditions and shifts to yellow as the solution becomes basic, with its transition occurring around pH 3.1 to 4.4. The statement that phenolphthalein is colorless below ~8.2 and pink above matches this behavior. The other choices mix up the colors or the pH ranges: phenolphthalein does not turn blue in acid, and methyl orange does not turn red in basic conditions. Also, the two indicators do not change color at the same pH.

Indicators reveal pH by changing color within specific ranges. Phenolphthalein stays colorless in acidic solutions and remains colorless until about pH 8.2, then turns pink in basic solutions as pH rises toward about 10. Methyl orange is red in strongly acidic conditions and shifts to yellow as the solution becomes basic, with its transition occurring around pH 3.1 to 4.4. The statement that phenolphthalein is colorless below ~8.2 and pink above matches this behavior. The other choices mix up the colors or the pH ranges: phenolphthalein does not turn blue in acid, and methyl orange does not turn red in basic conditions. Also, the two indicators do not change color at the same pH.