What is the Difference Between Red and Blue Litmus Paper

Litmus paper is a small strip of paper infused with a natural dye derived from lichens, which changes color in response to the pH of the solution it comes into contact with. Litmus paper is available in two common forms: red and blue litmus paper.

What is the difference between red and blue litmus paper? Red litmus paper indicates the presence of bases by turning blue, while blue litmus paper detects acids by changing to red.

Key Areas Covered

1. What is Red Litmus Paper
      – Definition, Features
2. What is Blue Litmus Paper
      – Definition, Features
3. Similarities Between Red and Blue Litmus Paper
      – Outline of Common Features
4. Difference Between Red and Blue Litmus Paper
      – Comparison of Key Differences
5. FAQ: Red and Blue Litmus Paper
      – Answers to Frequently Asked Questions

Key Terms

Red Litmus Paper, Blue Litmus Paper, Litmus Paper

What is Red Litmus Paper

Red litmus paper is a type of indicator used in chemistry to test for basic (or alkaline) solutions. If dipped in a basic solution, the red litmus paper will turn blue. If it is dipped in an acidic solution or neutral solution, there will not be any color change in the litmus paper. i e. it will remain red. The reason for the color change is a chemical reaction between the dyes and the molecules in the solution. In basic solutions, there are hydroxide ions (OH-) that interact with the dyes, causing them to shift color. Red litmus paper is made by soaking filter paper in a mixture of dyes extracted from lichens.

There are many advantages of red litmus paper. This litmus paper is inexpensive, easy to use, and provides a quick visual confirmation of a solution’s basic nature. Even though there are many advantages of using red litmus paper, it does not give an exact pH value. Therefore, for more precision, one has to use pH meters to get the pH value of the solution.

What is Blue Litmus Paper

Blue litmus paper is made by soaking paper in a natural dye extracted from lichens. It acts as a simple indicator of pH. When dipped into a solution, the dye in the paper reacts with the hydrogen ions (H+) present. These H+ ions are what define acidity – the more H+ ions, the stronger the acid.

If the solution being tested is acidic, the high concentration of H+ ions overpowers the dye in the blue litmus paper. This causes the paper to undergo a color change, turning from its original blue to a shade of red. The deeper the red, the stronger the acidity. In a neutral solution, where the concentration of H+ ions is balanced, the blue litmus paper will typically remain unchanged. However, some blue litmus paper might show a slightly purple hue in neutral environments. Basic or alkaline solutions have a low concentration of H+ ions. In such cases, the blue litmus paper won’t react and will retain its original blue color.

Though blue litmus paper gives a good indication of whether the solution is acidic, it does not give a numerical indication of the value of pH. Hence, pH meters must be used to determine the exact pH of the solution.

Similarities Between Red and Blue Litmus Paper

1. Both are made from filter paper that has been soaked in the same natural dye extract derived from lichens.
2. They act as pH indicators, giving a color change
3. Both do not indicate a numerical value for the pH of the solution.

Difference Between Red and Blue Litmus Paper

Definition

• Red litmus paper is a litmus paper that has a red color while blue litmus paper is a litmus paper that has a blue color.

Color Change

• Red litmus paper turns blue in the presence of a base, while blue litmus paper turns red in the presence of an acid.

Use

• Red litmus paper is used to identify bases, whereas blue litmus paper is used to identify acids.

Response to pH

• Red litmus paper remains red in neutral or acidic conditions, while blue litmus paper remains blue in neutral or basic conditions.

Conclusion

In conclusion, red and blue litmus papers serve as valuable tools in chemistry for quickly identifying the nature of solutions. Red litmus paper indicates the presence of bases by turning blue, while blue litmus paper detects acids by changing to red. This is the difference between red and blue litmus paper.

FAQ: Red and Blue Litmus Paper

1. What is blue litmus paper for?

Blue litmus paper is used to determine whether a solution is acidic or not. When dipped in an acidic solution, it turns a red color. This helps to identify whether a solution is acidic or not.

2. What does it mean when red litmus paper stays red?

When red litmus paper stays red, this means the solution in which it is dipped is either an acid or a neutral solution and not a base.

3. What does red litmus to blue indicate?

Red litmus turning into blue indicates that the solution in which it is dipped is basic. Red litmus paper remains red in neutral or acidic conditions.

4. Can acid turn blue litmus to red?

Yes, an acid can turn blue litmus to red color. This is due to a chemical reaction happening between the dye in the litmus paper and the hydrogen ions in the solution.

5. Why does red litmus paper turn blue in ammonia?

Red litmus paper turns blue in the presence of ammonia because ammonia is a basic gas. Ammonia is a basic compound that can accept protons (H+) from water molecules, resulting in the formation of hydroxide ions (OH-) in solution. The hydroxide ions increase the pH of the solution, making it alkaline. Red litmus paper, which is sensitive to changes in pH, undergoes a color change from red to blue when exposed to alkaline conditions. 

Reference:

1. “Litmus.” Wikipedia. Wikipedia Foundation.
2. “Litmus Paper.” Vedantu.

Image Courtesy:

1. “Red and blue litmus papers” By Kanesskong – Own work (CC BY-SA 4.0) via Commons Wikimedia