Question

What is the difference between the universal indicator and phenolphthalein? Would it be easier or more difficult to determine the acidity of Coke/Pepsi or 7-Up/Sprite? Why?

Answer 1

universal indicator will change color as pH changes, continuously, therefore, it can be used for various pH ranges.

phenolphthalein is a precise indicator, will change color form 8-9 pH ranges... indicating there is acidic to basic pH change readily

For acidity of Coke + Pepsi

7-up / Sprite

they all use:

phosphoric acid + Carbonic acid

we needto neturalize acidic to --> basic media

it is much better to use phenolphthalein since it will change form acidic to basic media, which is the whole point of titration

if we do NOT know precie amounts, the concentration range will not help us with the indicator

therefore, choose phenolphthalein due to more precise pH change color/range