Detergents work in hard water
Charged ends that form no scum.
A cleaner for hard water
Soap forms scum in hard water. Another class of compounds, called detergents, can be used as cleansing agents instead.
What do you think detergents do in hard water?
What this lesson covers
The idea
Detergents, generally sodium salts of sulphonic acids or ammonium salts with chloride or bromide ions, have long hydrocarbon chains and charged ends that form no insoluble precipitates with calcium and magnesium ions, so they remain effective in hard water.
A cleaner for hard water
Soap forms scum in hard water. Another class of compounds, called detergents, can be used as cleansing agents instead.
What do you think detergents do in hard water?
- They stay effective and form no insoluble precipitate
- They form even more scum
- They stop working completely
Soap and detergent in hard water
Open every tab.
No scum, still effective
The charged ends of detergents do not make insoluble precipitates with calcium and magnesium ions, so detergents keep working in hard water.
Detergents, generally sodium salts of sulphonic acids or ammonium salts with chloride or bromide ions, have long hydrocarbon chains and charged ends that form no insoluble precipitates with calcium and magnesium ions, so they remain effective in hard water.
Notes
Detergents have long hydrocarbon chains and charged ends that form no insoluble precipitates with calcium and magnesium ions, so they remain effective in hard water.
Check yourself
What happens when a detergent meets the calcium and magnesium ions of hard water?
What do detergent molecules have?
Which is true about detergents in hard water?
What are detergents usually used to make?
- An insoluble scum forms. That happens with soap. The charged ends of detergents do not form insoluble precipitates.
- The detergent turns into soap. Detergents are another class of compounds, not soap. They form no insoluble precipitates and remain effective.
- No insoluble precipitate forms — correct. Yes!
- A long hydrocarbon chain and a charged end — correct. Yes!
- A short chain and no charge. Detergents have long hydrocarbon chains and charged ends.
- Only a ring of carbon atoms. Detergents have long hydrocarbon chains and charged ends.
- They need a larger amount, like soap. Soap needs a larger amount in hard water. Detergents remain effective.
- They remain effective — correct. Yes!
- They stop foaming completely. Detergents remain effective in hard water.
- Vinegar and pickles. Vinegar is a solution of acetic acid in water.
- Perfumes and flavourings. Perfumes and flavourings are made with esters.
- Shampoos and products for cleaning clothes — correct. Yes!