A 65-mL solution of 0.40 MAl(NO3)3 is mixed with 125 mL of 0.17 M iron(II) nitrate. Solid sodium

step 1 So let's start by finding the concentration of our ions. Okay, the concentration of the aluminum

A 65-mL solution of 0.40 MAl(NO3)3 is mixed with 125 mL of...

A $65-\mathrm{mL}$ solution of $0.40 \mathrm{MAl}\left(\mathrm{NO}_3\right)_3$ is mixed with 125 mL of 0.17 M iron(II) nitrate. Solid sodium hydroxide is then added without a change in volume. (a) Which will precipitate first, $\mathrm{Al}(\mathrm{OH})_3$ or $\mathrm{Fe}(\mathrm{OH})_2$ ? (b) What is $\left[\mathrm{OH}^{-}\right]$when the first compound begins to precipitate?

A $65-\mathrm{mL}$ solution of $0.40 \mathrm{MAl}\left(\mathrm{NO}_3\right)_3$ is mixed with 125 mL of 0.17 M iron(II) nitrate. Solid sodium hydroxide is then added without a change in volume.
(a) Which will precipitate first, $\mathrm{Al}(\mathrm{OH})_3$ or $\mathrm{Fe}(\mathrm{OH})_2$ ?
(b) What is $\left[\mathrm{OH}^{-}\right]$when the first compound begins to precipitate?

Key Concepts

Solubility Equilibrium

This concept involves the dynamic balance between a sparingly soluble solid and its ions in solution. In the context of precipitation reactions, solubility equilibrium determines whether a compound remains dissolved or forms a precipitate, based largely on the concentration of the ions and the solubility product constant.

Solubility Product Constant (Ksp)

Ksp is a specific equilibrium constant that applies to the dissolution of a sparingly soluble ionic compound. It is defined by the product of the ion concentrations, each raised to the power of their respective stoichiometric coefficients. Ksp values are used to predict whether a precipitate will form when the ionic product of the mixed solution exceeds the Ksp.

Reaction Quotient (Q)

The reaction quotient, Q, represents the current state of ion concentrations in a solution. By comparing Q to the Ksp of a particular compound, one can determine whether the solution is unsaturated (Q < Ksp), at equilibrium (Q = Ksp), or supersaturated (Q > Ksp), which in turn indicates if precipitation will occur.

Dilution and Mixing of Solutions

Mixing solutions changes the concentrations of the ions involved, which directly impacts the reaction quotient. Understanding dilution is essential in calculating how the volume increase from mixing solutions affects the ion concentrations, thereby influencing the point at which precipitation begins.

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