Which of the following is true about indicators?

Question 20 options:

They are weak acids or bases.

They are as accurate as a pH meter.

They maintain their colors across the range of pH values for which they are used.

all of the above

A indicator is a weak organic acid or a base which has shows different colors in acidic and basic mediums. The color change occurs when the weak acidic or basic indicator dissociates to give its respective conjugate base or conjugate acid.

Therefore the correct option would be Indicators are weak acids or bases.

Answer: Option (a) is the correct answer.

Explanation:

A substance that gives a visible change in color upon exposure to certain conditions is known as an indicator. Indicators are either weak acids or bases.

For example, phenolphthalein is an acid-base indicator which changes its color from colorless to pink in a basic solution at pH 8.2.

In a more basic solution, its color changes to bright purple.

Hence, indicators do not maintain their colors across the range of pH values for which they are used.

A pH meter tells exactly the pH value of a solution or substance. Whereas an indicator only tells whether a solution is acidic or basic.

Therefore, we can conclude that it is true about indicators that they are weak acids or bases.