Question

A solution gives the following colours with different indicators:

(A) Methyl orange $\Rightarrow$ yellow (B) Methyl red $\Rightarrow$ yellow (C) Bromo thymol blue $\Rightarrow$ Orange What is the pH of the solution?

• A. 5 to 7.5
• B. 6 to 6.3
• C. 4 to 4.5
• D. 5 to 6.5

Answer 1

The correct option is B

6 to 6.3

(a) the colour is methyl orange indicates that pH > 4.5 [Methyl orange is Red in acidic (pH < 4.2) and yellow in basic (pH > 4.5)]

(b) The colour in methyl red indicates that pH > 6.0. [Methyl red is pink in acidic (pH < 4.2) and yellow in basic (pH >6.0)]

(c) The colour in bromthymol blue indicates that pH > 6.3 [bromthymol blue is orange in acidic (pH < 6.3)and blue in basic (pH>7.5)]

Therefore, the pH of the solution is between 6.0 to 6.3.