# Come si calcola la concentrazione di ioni in una soluzione?

The concentrazione of ions in solution dipende dal rapporto molare between the dissolved substance and the cations and anions it forms in solution.

So, if you have a compound that dissociates into cations and anions, the minimum concentration of each of those two products will be equal to the concentration of the original compound. Here's how that works:

NaCl_((aq)) -> Na_((aq))^(+) + Cl_((aq))^(-)

Sodium chloride dissociates into Na^(+) cationi e Cl^(-) anions when dissolved in water. Notice that 1 mole of NaCl will produce 1 mole of Na^(+) and 1 mole of Cl^(-).

This means that if you have a NaCl solution with a concentration of "1.0 M", the concentration of the Na^(+) lo sarà "1.0 M" and the concentration of the Cl^(-) lo sarà "1.0 M" come pure.

Let's take another example. Assume you have a "1.0 M" Na_2SO_4 soluzione

Na_2SO_(4(aq)) -> 2Na_((aq))^(+) + SO_(4(aq))^(2-)

Notare che la Talpa ratio between Na_2SO_4 e Na^(+) is 1:2, which means that 1 mole of the former will produce 2 moles of the latter in solution.

This means that the concentration of the Na^(+) ions will be

"1.0 M" * ("2 moles Na"^(+))/("1 mole Na"_2"SO"_4) = "2.0 M"

Think of it like this: the volume of the solution remains constant, but the number of moles doubles; automatically, this implies that the concentration will be two times bigger for that respective ion.

Here's how that would look mathematically:

C_("compound") = n_("Compound")/V => V = n_("compound")/C_("compound")

C_("ion") = n_("ion")/V = n_("ion") * 1/V = n_("ion") * C_("compound")/n_("compound")

C_("ion") = C_("compound") * n_("ion")/n_("compound")

As you can see, the mole ratio between the original coumpound and an ion it forms will determine the concetration of the respective ion in solution.