Urgent: pH of washing powders and soaps?! (1 Viewer)

[2opinion8d]

Hey I've got a chem prac due tommorow and I need a bit of help on a discussion question...

"Explain why most soaps and washing powders have a pH of above seven"

I've done some research and this is my answer

Most soaps and washing powders have a pH above 7 to help control the acidity of the water that they are used in. For example, solid detergents usually contain sodium carbonate or sodium bicarbonate to maintain pH by neutralising any acidic materials that may enter the wash water. Another reason why soaps and washing powders have pH values of above seven is to prevent precipitates forming when the soap and detergents react with the calcium and magnesium ions in hard water

is that okay? Can anyone elaborate on the hard water bit... thanx!

 

[pLuvia]

Soaps are synthesised by a fat (eg glycerol tristearate) and a base (eg sodium hydroxide) to form glycerol and a salt (sodium stearate)

Hence why they are basic due to the presence of the sodium hydroxide which is a very strong base, quite corrosive as well

 

[Forbidden.]

I'm sure your bowl with some salsa would be much more easily cleaned with a detergent containing bases than one containing acids.

A discussion question like that doesn't require too much writing, your answer should be sufficient.

 

[xiao1985]

gj pLuvia...

that's the gist of it...

 

[Itike]

I have a question from the same prac-“Like HCl and H2SO4, water also contains the element hydrogen. How do you know that water is not an acid?”

 

[xiao1985]

it is... and at the same time, it's also a base...

water self ionises to a certain extent

H2O + H2O <-----> H30+ + OH -

cept it happens to a very small degree ...

 

[kloudsurfer]

I have a question from the same prac-“Like HCl and H2SO4, water also contains the element hydrogen. How do you know that water is not an acid?”

I did the same prac. I asked my chem teacher and he said what ^xioa^ said.

However, the official answer from the prac manual is simply that it is because water has a pH of 7.

Stupid, i know.