Question

what is the working pH range for methyl orange?
A. $6.4-8.0$
B. $1.2-2.8$
C. $3.1-4.4$
D. $6.0-7.8$

Answer 1

Hint: Chemical indicators are the substance that provides a clear sign or an indication of color change of the absence or presence of concentration of species such as an acid or base in the solution. There are two types of indicators: natural and artificial.

Complete step by step answer:
The chemical indicators are used in the titrations in order to check whether the given solution is acidic, basic or neutral in nature.
There are two types of indicators: artificial and natural.
a.Artificial indicators:
Litmus paper, phenolphthalein, methyl orange and many more.
1.Litmus paper
There are two types of litmus paper: red litmus and blue litmus.
Red litmus paper is used to check whether the solution is basic or not.
Blue litmus is used to check whether the solution is acidic or not.
If red litmus turns blue then the solution is basic and if blue litmus paper turns red then it means that the solution is acidic.
2.Phenolphthalein indicator
Phenolphthalein is basic in nature.
It is used to check whether the solution is basic or not.
If the solution is basic in nature then the color of the solution will turn pink and after the neutralization the color changes to colorless.
Its working pH range is $8.3-10.0$ .
Phenolphthalein is used widely in acid-base titrations.
3.Methyl orange indicator.
Methyl orange is a type of pH indicator.
It is used to determine the pH of the solution.
The working pH range of methyl orange is from $3.1-4.4$ .
It shows yellow color in basic solution and red color in acidic solution.
It is mostly used for acidic solutions.
b.Natural indicators
Examples of natural indicators are turmeric, cherries, berries and many more.
Turmeric
When it is applied to an acidic medium the turmeric turns into yellow color.
When it is applied on a basic medium the turmeric turns red.
Cherries
When it is added to an acidic medium it turns red color and when in basic medium it turns blue to purple color.
Berries
In the acidic medium it turns red and in the basic medium it turns blue to purple.
Therefore, the working pH range of methyl orange is from $3.1-4.4$ .

So, the correct answer is Option C.

Note: Indicators are mostly used to detect the endpoint of titrations. The dissociation of hydrogen ions in the solution results in the color change in the solution. Indicators detect the presence of hydrogen and hydroxide ions in the solution.