NCERT Solution for Class Tenth Science Chapter 4
Carbon and its Compounds
CBSE NCERT Book Session-2022-2023
Intext Questions
Page No-21
Questions No-11
What change will you observe if you test soap with litmus paper (red and blue)?
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NCERT Solution for Class Tenth Science Chapter 4
Carbon and its Compounds
CBSE NCERT Book Session-2022-2023
Intext Questions
Page No-21
Questions No-11
Since soap is basic in nature, it will turn red litmus blue. However, the colour of blue litmus will remain blue, because soap is sodium salt of fatty acid. It is obtained by treatment of oil with caustic soda. Sodium stearate is thus a salt of weak acid and strong base, so it is alkaline in nature.
When you test soap with litmus paper, you may observe a change in the color of the litmus paper, depending on the type of soap and its pH level:
1. Red Litmus Paper:
. If the soap is acidic, the red litmus paper will remain red because it does not change color in acidic solutions.
If the soap is neutral or slightly alkaline, the red litmus paper may turn blue, indicating a shift towards a more alkaline pH.
2. Blue Litmus Paper:
. If the soap is alkaline, the blue litmus paper will remain blue because it does not change color in alkaline solutions.
. If the soap is neutral or slightly acidic, the blue litmus paper may turn red, indicating a shift towards a more acidic pH.
The color change in the litmus paper is due to the pH-sensitive compounds in the paper that react with the acidity or alkalinity of the substance being tested. Soap is generally slightly alkaline, so it is likely to turn red litmus paper blue. However, the exact pH of soap can vary depending on the formulation and brand.