Problem: 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?

FREE Expert Solution

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)is:


Q=productsreactants=[Mg2+][OH-]2


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Problem Details

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 tutors have indicated that to solve this problem you will need to apply the Selective Precipitation concept. If you need more Selective Precipitation practice, you can also practice Selective Precipitation practice problems.

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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.