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Basic solutions

Identify the list in which all salts produce a
basic aqueous solution.
1. AlCl3, Zn(NO3)2, KClO4
2. AgNO3, NaCHO2, CrI3
3. KCH3COO, NaCN, KF
4. CH3NH3Cl, KNO3, NaBz (sodium ben-
zoate)
5. NH4Cl, C6H4NH3NO3, FeI3

I thought it was 1 is that correct?

From knowledge, HClO4 is a strong acid, KOH is a strong base so the salt KClO4 should not affect H+:OH- ratio in water. Should be pH=7

So look at the make up of the salts - you want the list with all salts the salts of weak acid and strong base
 

3 seems to be correct ?

3 is the only one that contains salts of strong bases and weak acid, so should form basic solutions in water.
In case you did not know, the part of the salt from the weak acid removes some of the H+ ions from the water equilibrium causing changes in this equilibrium that result in [OH-] increasing.

H2O(l)    H+[aq] + OH-(aq)  (pH = 7 because the ions are in equal numbers.
However the presence of ions such as CH3COO- alter this ratio
CH3COO-(aq) + H+(aq) CH3COOH
More water ionises and [OH-] increases making the pH in water >7

ok that makes sense




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