Hi.
I would really appreciate some kind soul helping me figure out this simple question: For a substance, how do you know if it's acid or alkali? When the formula is given. For instance, sodium carbonate is an alkali.
Is there a general rule that determines whether something is acid or alkali-for instance something like 'all carbonates are alkali' ??
If there are such general rules, please post me those 'cause at the moment, I have no clue!
Thanks
I'm interested to know too, I just remember that an alkali is a base that can be dissolved in water?
The only acids you need to be familiar with are Hydrochloric acid and Sulfuric acid. Alkalis often have hydroxides at the end of their name e.g Sodium Hydroxide. The hydroxide stands for the OH- hroup attached to them. Acids only have H+ and no OH- group. For example, sulfuric acids molecular formula is H2SO4, it contains a H+ group but no OH-. Although it contains both oxygen and hydrogen they are seperate and do not form a hydroxyl group.
the bonsted lowry defination of an acid is something that can donate a proton (H+ ion) and a base/alkali can accept a H+.
so look for something that can donate a H or accept one. i don't know what level you're at but if your a level then you should be able to notice whether it can accept it or not.
its not just as simple as H+ and OH- 's because water arguably has both, and yet can act as a very very weak acid.
Bronsted Lowry theory states that an acid is a proton donator and a base/alkali is a proton aceptor.
Acids are proton donors and alkalis are proton acceptors....
Remember that a H+ is a proton...
Alkali blue, acid red? LOOL I haven't done Chem in about 2 years.
There are three definitions of acids/bases:
Arrhenius: As defined by Arrhenius, acid–base reactions are characterized by Arrhenius acids, which dissociate in aqueous solution to form hydrogen ions (H+) and Arrhenius bases, which form hydroxide (OH-) ions
Bronsted-Lowry: Acid is an H+ donor, base is an H+ acceptor. eg an alcohol can lose it's H from the OH and an amine can pick up an H.
Lewis: Acid - lone pair acceptor, base - lone pair donor. For example you may have heard of AlCl3 being described as a lewis acid
Each of these definitions includes substances defined by the ones above, but is a more broad definition.
Thanks everybody-keep posting!!
Use something called the PH scale and then add universal indicator to the substance and it will turn anywhere from red to purple. Red being very acidic and purple being very alkali and green being neutral
Basically acids are H+ whereas; alkali are OH-. Also if it ends in hydroxide it probs is a alkali.
alkali is the one with OH- ions
acid is the one with H+ ions
I too have an irresistible urge to post in this most ancient of threads.
I'd like to point out that acid solutions contain the OH- ion.
And I'd be correct too.
That'll confuzzle a lot of you.
Oh and whilst I'm in the confuzzling mood, a solution with a pH of more than 7 can be acidic.
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