![]() ![]() Barium sulfate, on the other hand, is insoluble (see rule 4). Lithium nitrate is a salt of a group 1 cation with the eminently soluble nitrate anion, and it’s soluble in water. The possible salts in this case are BaSO 4 and LiNO 3 (the ions involved are Ba 2+, Li +, NO 3 –, and SO 4 2–). ![]() To write the new salts that could form from these reactants, we simply trade either the cations or the anions while taking care to balance charges. Subject the new salts to the solubility rules to determine the solubility of each in water.Ĭonsider the combination in aqueous solution of barium nitrate, Ba(NO 3) 2, and lithium sulfate, Li 2SO 4.Write down the two new salts formed from combinations of the reactant ions.Hence, to determine the results of a potential precipitation reaction, we need to follow two steps. Salts that are insoluble according to the rules will precipitate out of solution when the cation and anion are both present. The solubility rules are a powerful tool when it comes to precipitation reactions. Predicting the Result of Mixing Two Salt Solutions According to the solubility rules sodium nitrate is a soluble salt, so we should expect it to stay in solution. Note also that the counterions to silver and chloride, sodium cation and nitrate anion, remain in solution. They do so spontaneously because the energy released by ionic-bond formation is greater than the energy required to ruin solvation. Note that the combination of a silver salt and a chloride salt in water allows the silver and chloride ions to pair up. This solid is silver chloride, a salt which is insoluble in water itself. ![]() However, when an aqueous solution of silver nitrate is mixed with a solution of sodium chloride, a gray solid, or precipitate, comes out of the water. Sodium chloride (NaCl) is of course also soluble in water. Silver nitrate (AgNO 3) is soluble in water-it's a nitrate, after all. Let's look briefly at an example of a precipitation reaction. This process is the opposite of dissolution (literally its thermodynamic reverse), and it's called precipitation. As a result, ionic bonds will form spontaneously, and the ionic solid will come out of solution as the ions pair up. Will the cation and anion stay in solution? Thermodynamically, it's clear that the formation of strong ionic bonds more than compensates for the loss of ion-dipole interactions around each ion (that's what we mean when we say that the ionic bonds are "strong"). We might wonder, then, what happens when we use two separate salts to introduce into solution a cation and anion that bond strongly to one another. We've seen that although many ionic salts dissolve in water, those characterized by strong ionic bonds do not. ![]()
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