[lolajune]

What is the difference between these two equations?

CaCl2 (s) --water--> Ca2+ (aq) + 2 Cl- (aq)

CaCl2 + H2O --> CaO + 2HCl

What circumstances are needed to produce calcium oxide and hydrochloric acid?

[Big-Daddy]

I don't think your second reaction happens ... if it does, then what's going on is that CaO is being precipitated out leaving H+ and Cl- ions in the water. But I doubt CaO would be very easily precipitated out (haven't checked up the Ksp data though).

[lolajune]

I don't think your second reaction happens ... if it does, then what's going on is that CaO is being precipitated out leaving H+ and Cl- ions in the water. But I doubt CaO would be very easily precipitated out (haven't checked up the Ksp data though).

What if the pH of the water was 7.35 to 7.45 and had NaCl?

[Big-Daddy]

I don't think your second reaction happens ... if it does, then what's going on is that CaO is being precipitated out leaving H+ and Cl- ions in the water. But I doubt CaO would be very easily precipitated out (haven't checked up the Ksp data though).

What if the pH of the water was 7.35 to 7.45 and had NaCl?

Explicitly not ... having a high pH means the concentration of H⁺ will be even lower, which makes it even less likely that we are forming HCl molecules out of H⁺ and Cl^-. As for CaO, shouldn't be relevant ... CaO if it is indeed solid will react promptly with the water to produce Ca(OH)₂ anyway.