Chemistry homework help
Chemistry homework help. The of depends on the 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^(+)## cations and ##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^(+)## ion will be ##”1.0 M”## and the concentration of the ##Cl^(-)## ion will be ##”1.0 M”## as well.
Let’s take another example. Assume you have a ##”1.0 M”## ##Na_2SO_4## solution
##Na_2SO_(4(aq)) -> 2Na_((aq))^(+) + SO_(4(aq))^(2-)##
Notice that ratio between ##Na_2SO_4## and ##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.
Here’s a link to another answer on this topic:
http://socratic.org/questions/how-do-you-calculate-the-number-of-ions-in-a-solution?source=search
