Home
Class 12
CHEMISTRY
Why do soaps not work in hard water ?...

Why do soaps not work in hard water ?

Text Solution

Verified by Experts

Soaps are sodium or potassium salts of long-chain fatty acids. Hard water contains calcium and magnesium ions. When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids. These insoluble salts separate as scum.

This is the reason why soaps do not work in hard water.
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • CHEMICAL KINETICS

    NCERT|Exercise SOLVED EXAMPLE|1 Videos

  • COORDINATION COMPOUNDS

    NCERT|Exercise Exercise|41 Videos

Similar Questions

Explore conceptually related problems

Both soap and detergent are some type of salts. What is the difference between them? Describe in brief the cleansing action os soap. Why do soaps not form lather in hard water? List two problems that arise due to the use of detergents instead of soaps.

Both soap and detergent are some type of salts. What is the difference between them? Describe in brief the cleansing action of soap. Why do soaps not form lather in head water? List two problems that arise due to the use of detergents instead of soaps .

Knowledge Check

  • Soaps do not work in hard water containing calcium and magnesium ions because

    A
    `Ca^(2+) and Mg^(2+)` ion form insoluble calcium and magnesium salts in the form of scum
    B
    `Na^(+) and K^(+)` present in soap react with `Ca^(2+) and Mg^(2+)` and hinder cleansing process
    C
    a large amount of soap is to be used in presence of ` Ca^(2+) and Mg^(2+)`
    D
    scum formed by combination of `Na^(+),Ca^(2+) and Mg^(2+)` stick to the cloth and are not removed on agitations.

  • Soaps are the detergents used since long. Soaps used for cleansing purpose are sodium or potassium salts of long chain fatty acids such as stearic acid, palmitic acid. These cannot be used with hard water. Synthetic detergents are cleansing agents which have all the properties of soap but which actually do not contain any soap. These can be used both in soft water and hard water as they give foam even in hard water. Which of the following is called invert soap?

    A
    Sodium stearate
    B
    Cetyl trimethyl ammonium bromide
    C
    Sodium lauryl sulphate
    D
    Tetraethyl ammonium chloride

    • Similar Questions

    Explore conceptually related problems

    Is it true that soaps do not work well with hard water ?

    Why soap is ineffective with hard water

    In Villages, people often wash their clothes with well water. They have to rub a lot of soap before lather is formed. This is because well water is hard water. Thus, a lot of soap is wasted. However, if they use detergent powder in place of soap, lather is formed easily and wastage is less. Now, answer the following questions : (i) What values are expressed in the above paragraph? (ii) Why soap does not form lather with hard water?

    In the laboratory of a school , the sample of hard water is not available " to study the comparative cleaning capacity of a sample of soap in soft and hard water". Which salt from the laboratory can be added to tap water to make it hard ? In the experiment how is cleaning capacity of soap compared ?

    When soap is added to hard water, it reacts with the salts to form a scum. Why does this scum form ?

    When soap is added to hard water, it reacts with the salts to form a scum. Why does this scum form ?

    Home
    Profile