NESA Chemistry Solution Equilibria

Leaching is a physical separation process based on solubility, not a chemical reaction with the toxins.

Submerging food in water does not prevent decomposition; the primary purpose of this specific process is to remove toxins, not preserve the food.

Breaking down compounds involves chemical changes (like cooking or fermentation), whereas leaching is a physical process used to extract and wash away existing toxic compounds.

The enthalpy change (whether a reaction is exothermic or endothermic) determines the thermodynamics of the reaction, not its kinetics or rate. Highly exothermic reactions can still be very slow.

Reactions requiring the simultaneous collision of many types of particles are statistically less likely to occur, which would typically result in a slower reaction rate, not a faster one.

The prompt explicitly states the reaction is rapid at room temperature, indicating that an external heat source like a flame is not required to overcome the activation energy.

Ammonium ($NH_4^+$) is a cation and will not react or form a precipitate with either $Pb^{2+}$ or $Na^+$ cations.

All nitrate ($NO_3^-$) salts are soluble in water, meaning no precipitate will form with either $Pb^{2+}$ or $Na^+$ to help distinguish them.

Most acetate ($CH_3COO^-$) salts, including lead(II) acetate and sodium acetate, are soluble in water, so no visible reaction or precipitate will occur.

This option incorrectly assumes the iodide concentration is $2 \times 0.1$ and fails to square the iodide concentration in the $K_{sp}$ expression.

This option incorrectly assumes the iodide concentration from NaI is $2 \times 0.1$. NaI only produces one iodide ion per formula unit, so the initial $[\text{I}^-]$ is $0.1 \text{ mol L}^{-1}$.

This option forgets to square the iodide concentration. The $K_{sp}$ expression for $\text{PbI}_2$ is $[\text{Pb}^{2+}][\text{I}^-]^2$, so the denominator must be squared.

While lead(II) chloride ($\text{PbCl}_2$) is sparingly soluble, it is significantly more soluble than silver chloride, allowing trace amounts of $\text{Pb}^{2+}$ to remain in solution.

Magnesium chloride ($\text{MgCl}_2$) is highly soluble in water, making $\text{Mg}^{2+}$ one of the most abundant dissolved ions in the ocean.

Potassium chloride ($\text{KCl}$) is highly soluble in water, meaning $\text{K}^+$ ions can easily remain dissolved in the ocean.

This incorrect result comes from improperly setting up the solubility product expression as $K_{sp} = 2s^3$ instead of the correct $K_{sp} = 4s^3$ for a 1:2 electrolyte.

This error occurs when the coefficient of 4 is omitted from the solubility product expression, incorrectly using $K_{sp} = s^3$ instead of $4s^3$ to find the molar solubility.

This is the mass of lead(II) iodide that would dissolve in exactly 1.0 L of water. This mistake happens if you forget to multiply the molar solubility by the actual given volume of 0.375 L.

Pure solids, like $\mathrm{Ca(OH)_2(s)}$, have a constant concentration and are excluded from equilibrium constant expressions.

This expression incorrectly places the reactants in the numerator and products in the denominator, and it incorrectly includes the pure solid $\mathrm{Ca(OH)_2(s)}$.

This is the equilibrium constant expression for the reverse reaction (precipitation), not the forward dissolution reaction.

Incorrect. This expression fails to raise the concentration of $\text{AgNO}_3$ to the power of its stoichiometric coefficient, which is 3.

Incorrect. This expression incorrectly places reactants over products and includes the solid $\text{AgCl}$, which should be excluded from the equilibrium expression.

Incorrect. Although it correctly places products over reactants, it incorrectly includes the solid $\text{AgCl}$, which must be omitted from equilibrium expressions.