A beaker contains a saturated solution of in equilibrium with undissolved at

CHEMISTRY · Single correct · AP · Chemistry · Equilibrium · Equilibrium

Problem

A beaker contains a saturated solution of

\text{AgCl}

in equilibrium with undissolved

\text{AgCl}

25^\circ\,\text{C}

. After solid

\text{NaCl}

is added and allowed to dissolve completely, the concentration of

\text{Ag}^+

in the solution is found to decrease sharply. Which of the following provides the best explanation for this observation? (a) Because

\mathrm{NaCl}

is much more soluble than

\mathrm{AgCl}

, the highly soluble salt forces

\mathrm{AgCl}

to leave the solution and precipitate. (b) The added

\mathrm{Na^+}

ions lower the ionic strength of the solution, so the solubility product of

\mathrm{AgCl}

is exceeded and the salt precipitates. (c) The extra

\mathrm{Cl^-}

ions shift the dissolution equilibrium of

\mathrm{AgCl}

toward the solid according to Le Châtelier’s principle, so

\mathrm{Ag^+}

is removed from solution. (d) Excess

\mathrm{Cl^-}

reacts with

\mathrm{Ag^+}

to form the soluble complex ion

\mathrm{AgCl_2^-}

, reducing the measured concentration of free

\mathrm{Ag^+}