Question

Colour of methyl orange in alkali condition is
A. Orange
B. Yellow
C. Red
D. Blue

Answer 1

Hint: To solve this question, first we get to know that methyl orange is one of common color indicators used in chemical laboratories. Now, we need to understand the concept of a chemical indicator. A chemical indicator is a substance that indicates a visible sign usually in terms of color changing in the absence or presence of any kind of threshold energy of any chemical species like an acid or an alkali in a solution.

Complete step by step answer:
 As we know that an indicator is a substance that indicates color change in the addition of any kind of threshold concentration. For example let’s consider methyl yellow aims on imparting a yellow color to a solution containing an alkali.
So, we know methyl orange is an indicator due to which it is frequently used for performing titration experiments in laboratories. Thus, it is responsible for changing the color of the solution in respect to the pH value of the solution. So, when methyl orange is taken then it is reddish orange in color due to the acidic conditions. But in the alkali conditions the color of this reddish orange color changes into yellow color.
Let’s pay a little attention to the pH range of methyl orange indicator which lies between 3.1 to 4.5 \[pH\]. So, the pH will be below 3.1 when it is in red color and as soon as the pH rises above 4.5 the color changes to yellow
And hence the correct answer is (option B).

Additional information:
The chemical formula of methyl orange is \[{C_{14}}{H_{14}}{N_3}Na{O_3}S\].

Note:
We must know that an indicator will always show a different color in an acidic and basic medium. Methyl orange is a common indicator used in laboratories. Litmus paper and phenolphthalein are also used in laboratories as indicators.