Consider two separate

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

Problem

Consider two separate, identical beakers that each contain a saturated solution of

\text{BaSO}_4

in equilibrium with excess solid

\text{BaSO}_4

at a fixed temperature. To the first beaker, a small amount of

\text{Ba(NO}_3)_2

is added; to the second, an equal ionic-strength amount of

\text{NaNO}_3

is added. Which statement correctly compares the effects of the two additions on the solubility of

\text{BaSO}_4

? (a) Both salts decrease the solubility of

\text{BaSO}_4

by the same amount because they contribute identical ionic strength to the solution. (b) The addition of

\text{NaNO}_3

increases the solubility of

\text{BaSO}_4

because

\text{Na}^+

reacts with

\text{SO}_4^{2-}

to form soluble

\text{Na}_2\text{SO}_4

, reducing sulfate concentration. (c) The addition of

\text{Ba(NO}_3)_2

decreases the solubility of

\text{BaSO}_4

more than the addition of

\text{NaNO}_3

because

\text{Ba}^{2+}

is a common ion that shifts the equilibrium toward the solid. (d) The addition of

\text{Ba(NO}_3)_2

increases the solubility of

\text{BaSO}_4

because the higher ionic strength screens electrostatic attractions in the crystal lattice.