Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Jules18 on September 01, 2009, 05:58:39 PM
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Here's the question:
The ionization constant for acetic acid is 1.8E-5; that for hydrocyanic acid is 4E-10. In 0.1 M solutions of sodium acetate and sodium cyanide, it is true that:
And the answer is:
[OH-] of the sodium acetate solution is less than that of the sodium cyanide solution.
Which makes sense to me, because acetic acid is the stronger acid. But there's another option in the list that it says is NOT true:
[H+] exceeds [OH-] in each solution.
I thought this might be true, because both are solutions of chemicals that were referred to as acids.
Am I missing the definition of an acid?
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Do you really think that NaCN is an acid? Looks like a salt to me:
NaOH+HCN=NaCN+H2O
so if you consider its hydrolysis (and the reagents in the reaction above) you'll see why [OH-] exceeds [H+]... ;)
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... if it's not an acid, why did the question refer to it as an acid?
Bad wording... ?
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No, bad understanding of the problem on your side.
There is a weak acid - say, acetic acid.
It is neutralized and creates a salt - acetate.
Acetate anion is a conjugate base of acetic acid.
So solutions we are talking about are not solutions of acids - but of their conjugate bases.
Solution of base is usually alkalic.
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Thanks, that makes sense to me.
Except, does "alkalic" refer to group 1 or group 2 elements?
Do you mean that most chemicals that have those elements are bases?
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I mean alkalic like "having high pH".