We’re being asked to determine if a precipitate will form when in a solution that is 1.0 x 10-1 M CaCl2 and 1.0 x 10-9 M AgNO3.
For this, we need to compare the reaction quotient (Q) vs. the solubility product constant (Ksp).
Recall that when:
• Q > Ksp: the solution is supersaturated and a precipitate will form. Reactants are favored.
• Q = Ksp: the solution is at equilibrium and no precipitate will form.
• Q < Ksp: the solution is unsaturated and no precipitate will form. Products are favored.
The expected precipitate is AgCl. The sulfate ion, Ag+, has a charge of +1. Cl then has a charge of -1.
The dissociation of Ag2SO4 in water is as follows:
AgCl(s) ⇌ Ag+(aq) + Cl–(aq)
The Ksp of AgCl at 25 °C is 1.6 x 10-10. Consider a solution that is 1.0 x 10-1 M CaCl2 and 1.0 x 10-9 M AgNO3.
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What scientific concept do you need to know in order to solve this problem?
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