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Author Topic: Acids and Bases  (Read 589 times)

Cat

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Acids and Bases
« on: March 21, 2010, 07:08:09 PM »
Hello everyone!  :)
I need help with the following question:
1)
I have trouble following this paragraph:

"_It is important to realize that the stronger the acid, the weaker its conjugate base and the stronger the base, the weaker its conjugate acid_. For example the weak acid HF has a conjugate base F- that has a strong tendency to attract a proton to form HF. You need to understand that the conjugate base of a weak acid is a weak base, not a strong base in water. Similarly, the conjugate acid of a weak base is a weak acid, not a strong acid" ??? ??? ???

2) From reading the sample exercises in my book, I have the feeling that I should know a list of strong acids and bases, weak acids and bases...is that true? I'm not sure which list to study though.

Thank you!
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Acids and Bases
« on: March 21, 2010, 07:08:09 PM »
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uma

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Re: Acids and Bases
« Reply #1 on: March 22, 2010, 02:15:39 AM »

"_It is important to realize that the stronger the acid, the weaker its conjugate base and the stronger the base, the weaker its conjugate acid_. For example the weak acid HF has a conjugate base F- that has a strong tendency to attract a proton to form HF. You need to understand that the conjugate base of a weak acid is a weak base, not a strong base in water. Similarly, the conjugate acid of a weak base is a weak acid, not a strong acid" ??? ??? ???

The second part of the above statement appears to be wrong.
Weak acids and weak bases set up an equilibrium with water
HA + H2O <----> A - + H3O+
Equilibrium lies on the left side as HA is a weak acid and has very poor dissociation in water. This means that concentration of HA is more than the concentration of A- at the equilibrium.
 If you visualize this equilibrium from the right side then you can say that A- has a strong tendency to accept a proton from H3O+ and hence is a strong base.

Now A- is the conjugate base of HA.
I think that from the above explanation, a weak acid will give you a strong conjugate base.
Same thing is applicable for a weak base.
yes you need to know names of weak /strong acids and bases.Do not worry list is not too long .
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Re: Acids and Bases
« Reply #1 on: March 22, 2010, 02:15:39 AM »
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