antacid?

[Carlos26]

hello, I was wondering if anyone could differentiate an antacid and an alkaline because as far as I can see, there's no alkalinic substances in an antacid and can't see how it would be able to neutralise acid.  thanks.

[Peter Pedant]

Alkaline is anything a pH of above 7. Below seven it is an acid. Pure water has a pH of almost exactly seven.

An antacid is a drug which counteracts stomach acid. Stomach acid has a pH of arund 2.5 - that is, de- daaah, see above, it is acid. The antacids you've been readin about are all sodium combined with a weak acid, which means that they are weakly alkaline, and as such can counter act the stomach acid.

Do not take alkali such as Sodium hydroxide as an antacid, it is poison. and if you are a kid for chrissakes dont give other kids alkali as 'a joke'.

[incitatus]

The effect peter is referring to is buffering.  look up beffer solution.  However many antacid tablets contain calcium carbonate, a substance which is not an alkali but a base.  Bases react with acids to form neutral solutions.  alkalis are merely water soluble bases.