Page 17 - E-Science Prep1 2024-2025 t2 Unit1_Neat - Copy

Unit 1 Lesson (3): Chemical indicators & Salts

Chemical substances whose color differs in acidic medium from that
in alkaline medium.

To differentiate acidic / alkaline / neutral substances.

It is used in the composition of litmus strips as its color changes
according to the type of medium.

Effect of litmus indicators In acidic medium (weak /
strong) the blue strip turns
red due to the effect of H+

In alkaline medium the
red strip turns blue due

to the effect of OH-
In neutral medium

(dist. water) the both red &
blue strips remain

unchanged as number of H+
= number of OH-

Litmus strips aren’t used to differentiate between strong & weak
acids as it gives the same color with both of them.

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Second Term