## Chemistry: The Central Science (13th Edition)

$Solubility = 1.817 \times 10^{-3} g/L$
$Kps (LaF_3) = 2 \times 10^{-19}$ 1. Write the Kps equation: $Kps (LaF_3) = [La^{3+}] * [F^-]^3$ $[La^{3+}] = x$ $[F^-] = 3x$ 2. Now, find the solubility: $2 \times 10^{-19} = [x] * [3x]^3$ $2 \times 10^{-19} = x * 27x^3$ $2 \times 10^{-19} = 27x^4$ $7.407 \times 10^{-21} = x^4$ $x = 9.277 \times 10^{-6}M$ 3. Covert that number to g/L. $mm(LaF_3) = 138.9 + 19*3 = 195.9g/mol$ $mass = n(moles) * mm$ $mass = 9.277 \times 10^{-6} * 195.9$ $mass = 1.817 \times 10^{-3}g$ $Solubility = 1.817 \times 10^{-3} g/L$