Is pH Affected by Negative Ions in a Solution?

[christian0710]

1. If the statement ph=-log([H+] is true, then how come a solution can be acidic when carbonate is present? I have been told that even if carbonate does not accept H+ the solution will still be basic just by the presence of CO3(2-)? The confusion is this: ph only depends on [H+] then how come the presence of negative ions change the acidity level, even if they don’t actually accept hydrons?

I thought acidity levels change ONLY because CO3(-2) ----> H₂CO3 H+ is taken away.

 

[symbolipoint]

Carbonate anion is a base, but it can accept hydrogen ion and be protonated. If protonated, it is an acid, H₂CO₃, carbonic acid.

A solution of carbonic acid contains CO₃^-2, HCO₃^-1, H₂CO₃, and solvated H⁺ .

How does that work?
A solution of carbonic acid will give this incomplete reaction causing an equilibrated concentration of each reactant and product:
H₂CO₃ <------> H⁺ + HCO₃^-
AND
HCO₃^- <-------> H⁺ + CO₃^-2

Carbonic acid is a weak acid, so the presence of reactant is favored in contrast to the products.

 

[christian0710]

I see so HCO3(-) is preferred and therefore CO3(-2) takes away H+ from the solution, BUT is it tru that the presence of a acid or base in its acid or base form (with out reacting) would cause a solution to change acidity? And is it true that negatively charged ions can make a solution more basic without sucking up H+ ?? Or is it ONLY the presence of H+ and OH- that determines how acidic or basic a solution is?