Chapter 35: Problem 14

What are the colour changes observed during titration of a solution of sodium carbonate with hydrochloric acid using two drops each of phenolphthalein and methyl orange? What is the reason behind these colour changes?

Short Answer

Expert verified

The colour changes observed during titration are: from pink (phenolphthalein) and yellow (methyl orange) to colorless (phenolphthalein) and red (methyl orange). They occur due to the change in pH of the solution – when it becomes less than 8.2, phenolphthalein turns colorless and when it becomes less than 4.4, methyl orange turns red.

Step by step solution

Describe Initial Conditions

Initially, the sodium carbonate solution is alkaline in nature. When we add phenolphthalein, it turns pink because the pH is above 8.2. Similarly, methyl orange turns yellow as the initial pH is above 4.4.

Explain Color Change 1

As we start adding hydrochloric acid to the solution, it will react with sodium carbonate to neutralize it. When the pH drops below 8.2, phenolphthalein changes color from pink to colorless, indicating the completion of the reaction between hydrochloric acid and sodium carbonate.

Explain Color Change 2

Continuing to add more acid, when the pH drops below 4.4, methyl orange will change from yellow to red. This signifies that all the carbonate ions have been neutralized and the solution is now acidic.

Understand the Occurrence

The color changes occur due to the properties of the indicators used. Phenolphthalein changes color in the pH range of 8.0 to 10.0, and methyl orange changes color in the pH range of 3.1 to 4.4. These indicators detect the change in pH of the solution due to the acid-base neutralization reaction.

Unlock Step-by-Step Solutions & Ace Your Exams!

Full Textbook Solutions
Get detailed explanations and key concepts
Unlimited Al creation
Al flashcards, explanations, exams and more...
Ads-free access
To over 500 millions flashcards
Money-back guarantee
We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

Recommended explanations on Chemistry Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

What are the colour changes observed during titration of a solution of sodium carbonate with hydrochloric acid using two drops each of phenolphthalein and methyl orange? What is the reason behind these colour changes?

Short Answer

Step by step solution

Describe Initial Conditions

Explain Color Change 1

Explain Color Change 2

Understand the Occurrence

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Chemical Analysis

Kinetics

The Earths Atmosphere

Chemistry Branches

Physical Chemistry

Nuclear Chemistry

Study anywhere. Anytime. Across all devices.