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 kasse May12-08 05:03 PM

Salt that gives basic solution

1. The problem statement, all variables and given/known data

Explain why Na2CO3 gives a basic solution when dissolved in water.

3. The attempt at a solution

The cation is Na+ while the anion is CO32-. The cation has no affinity for neither protons nor hydroxide ions. The anion should have basic properties to make a basic solution. Does this mean that HCO3- is a weak acid? I cannot find it in my table of weak acids.

 symbolipoint May12-08 09:34 PM

Why basic? To be brief: Hydrolysis. HCO3-, is from Carbonic acid. Carbonic acid is a diprotic acid, and when you look for the dissociation constant you need to look for the one for carbonic acid which will show you the values for the first AND the second dissociations.

Carbonic Acid: $$$H_2 CO_3$$$

the first dissociation is stronger than the second dissociation.

 chemisttree May13-08 09:42 AM

Quote:
 Quote by kasse (Post 1727699) 1. The problem statement, all variables and given/known data Explain why Na2CO3 gives a basic solution when dissolved in water. 3. The attempt at a solution The cation is Na+ while the anion is CO32-. The cation has no affinity for neither protons nor hydroxide ions. The anion should have basic properties to make a basic solution. Does this mean that HCO3- is a weak acid? I cannot find it in my table of weak acids.
The pertinent reactions you need to conceptualize are:

1) CO3-2 + H2O <-------> HCO3- + OH-

and,

2) HCO3- + H2O <-----> H2CO3 + OH-

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