I was asked to consider the solubility for hydrated calcium sulfate in HCl.
The principal acid my proffesor had posted for the solution was [ CaSO4(hyrdrated) + HCl <--> H30^+ + Ca^2+ + SO4^2- ]. I guess what I'm asking is what happened to the Cl^- and why isn't it reacting with Ca^2+ to produce CaCl2. ? It's not a spectator ion right??? But if it is why?
It is a spectator ion, the chloride ion is in solution on both sides. CaCl2 is ionic, and is in ions in water solution.
correction: sulfate ion should be hydrogen sulfate ion
Yes, it is a spectator ion. Why? Because CaCl2 is soluble (it isn't a precipitate), it isn't a gas, and it isn't a weakly ionized substance. CaSO4 is more soluble in HCl than it is in water BECAUSE of k2 for H2SO4; i.e., HSO4^- = about 10^-2.
To understand why the chloride ion (Cl-) is a spectator ion in this reaction, let's break down the reaction and consider the solubility of hydrated calcium sulfate (CaSO4 · H2O) in HCl.
The given reaction is: CaSO4 · H2O + HCl ↔ H3O+ + Ca2+ + SO4^2-
The first thing to note is that this reaction is a double displacement reaction. The HCl is a strong acid, which means it will dissociate almost completely into its ions - H+ and Cl-. Similarly, the hydrated calcium sulfate will also dissociate into its ions - Ca2+, HSO4- (hydrogen sulfate ion), and H2O.
Now, let's focus on the solubility of hydrated calcium sulfate in HCl. The solubility of a compound depends on several factors, including the nature of the compound and the solution it is dissolved in. In this case, the presence of HCl in the solution plays a crucial role.
When hydrated calcium sulfate is dissolved in HCl, the chloride ion (Cl-) does not react with the calcium ion (Ca2+) to form calcium chloride (CaCl2) because the chloride ion is a spectator ion. A spectator ion is an ion that does not participate in the actual chemical reaction. It remains in solution unchanged before and after the reaction occurs.
In this case, the chloride ion (Cl-) is present on both sides of the reaction equation as it is part of HCl before and after the reaction. It does not undergo any chemical changes or combine with other ions to form a new compound. Therefore, it is considered a spectator ion.
The reason why CaCl2 does not form in this reaction is because CaSO4 is more soluble in HCl than it is in water. The presence of HCl increases the solubility of CaSO4 due to the presence of the sulfate ion (SO4^2-), which can react with the hydrogen ion (H+) in HCl to form HSO4- (hydrogen sulfate ion). This hydrogen sulfate ion has a slightly higher solubility in water compared to the sulfate ion, leading to increased solubility of CaSO4.
In summary, the chloride ion (Cl-) in HCl is a spectator ion in the given reaction. It does not react with the calcium ion (Ca2+) to form calcium chloride (CaCl2). Instead, it remains in solution unchanged as part of HCl. The solubility of hydrated calcium sulfate is increased in HCl due to the presence of hydrogen sulfate ion (HSO4-) formed from the reaction of HCl with the sulfate ion.
In the given reaction, the chloride ion (Cl^-) is indeed a spectator ion. A spectator ion is an ion that does not participate in the chemical reaction and remains unchanged throughout the process.
In this case, when hydrated calcium sulfate (CaSO4·xH2O) reacts with hydrochloric acid (HCl), the main reaction is between the hydrated calcium sulfate and the hydrogen ions (H+) from the hydrochloric acid. This reaction forms hydronium ions (H3O+) in solution, along with calcium ions (Ca2+) and sulfate ions (SO4^2-).
The chloride ions (Cl^-) from the hydrochloric acid are not directly involved in the reaction because the reaction primarily occurs between the sulfur-containing compound (calcium sulfate) and the acid (HCl). The chloride ions remain in the solution as spectator ions. They are present on both sides of the reaction equation and do not undergo any changes.
However, it is worth noting that the chloride ions (Cl^-) from the hydrochloric acid do contribute to the overall ionic strength of the solution. They are important for maintaining electrical neutrality and facilitating the solubility of the calcium sulfate compound. But as far as the specific reaction between hydrated calcium sulfate and hydrochloric acid is concerned, the chloride ions are not directly involved in producing calcium chloride (CaCl2).
In summary, the chloride ions (Cl^-) in hydrochloric acid are considered spectator ions in the reaction with hydrated calcium sulfate because they do not participate in the specific chemical changes involving the calcium and sulfate ions.