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 Mg(OH)2. The hydroxide ion, OH–, has a charge of –1. Mg then has a charge of +2.
The dissociation of Mg(OH)2 in water is as follows:
Mg(OH)2(s) ⇌ Mg2+(aq) + 2 OH–(aq)
The reaction quotient expression for Mg(OH)2 is:
Will a precipitate form when 100.0 mL of 4.0 X 10 -4 M Mg(NO3)2 is added to 100.0 mL of 2.0 X 10 -4 M NaOH?
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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition practice problems.