Question

Litmus, phenolphthalein and methyl orange are the common acid-base indicators. Basically these are organic dyes with characteristic colours. Litmus is the extract of the plant lichen. Phenolphthalein and methyl orange are synthesised in the laboratory. An indicator imparts a specific colour to an acidic solution and its colour changes. when the solution becomes basic or alkaline. The same applies to the basic solution as well. Will there be a color change if dilute HCl solution is slowly added to the solution of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and few drops of methyl orange?

Answer 1

We know that;

1. Methyl orange is used as an indicator.
2. It shows red color in acidic medium and yellow color in basic medium.
3. When it is added to the solution basic solution, the solution turns yellow.

Here we have a yellow solution of basic Na₂CO₃ containing Methyl orange indicator.

When a dilute solution of HCl is added to the above solution:-

1. A neutralization reaction takes place and the pH of the solution slowly becomes acidic.
2. The color of the solution slowly changes from yellow to Red-Pink color.

Thus, there will be a color change from yellow to red-pink.