Answer
a. $1.5 \times 10^{-3}M$
b. $2.3 \times 10^{-6}M$
c. $2.5 \times 10^{-7}M$
Work Step by Step
(a)
1. Write the $K_{sp}$ expression:
$ PbI_2(s) \lt -- \gt 1Pb^{2+}(aq) + 2I^-(aq)$
$1.4 \times 10^{-8} = [Pb^{2+}]^ 1[I^-]^ 2$
2. Considering a pure solution: $[Pb^{2+}] = 1x$ and $[I^-] = 2x$
$1.4 \times 10^{-8}= ( 1x)^ 1 \times ( 2x)^ 2$
$1.4 \times 10^{-8} = 4x^ 3$
$3.5 \times 10^{-9} = x^ 3$
$ \sqrt [ 3] {3.5 \times 10^{-9}} = x$
$1.517 \times 10^{-3} = x$
- This is the molar solubility value for this salt.
(b)
1. Write the $K_{sp}$ expression:
$ CdCO_3(s) \lt -- \gt 1Cd^{2+}(aq) + 1C{O_3}^{2-}(aq)$
$5.2 \times 10^{-12} = [Cd^{2+}]^ 1[C{O_3}^{2-}]^ 1$
2. Considering a pure solution: $[Cd^{2+}] = 1x$ and $[C{O_3}^{2-}] = 1x$
$5.2 \times 10^{-12}= ( 1x)^ 1 \times ( 1x)^ 1$
$5.2 \times 10^{-12} = 1x^ 2$
$5.2 \times 10^{-12} = x^ 2$
$ \sqrt [ 2] {5.2 \times 10^{-12}} = x$
$2.27 \times 10^{-6} = x$
- This is the molar solubility value for this salt.
(c)
1. Write the $K_{sp}$ expression:
$ Sr_3(PO_4)_2(s) \lt -- \gt 3Sr^{2+}(aq) + 2P{O_4}^{3-}(aq)$
$1 \times 10^{-31} = [Sr^{2+}]^ 3[P{O_4}^{3-}]^ 2$
2. Considering a pure solution: $[Sr^{2+}] = 3x$ and $[P{O_4}^{3-}] = 2x$
$1 \times 10^{-31}= ( 3x)^ 3 \times ( 2x)^ 2$
$1 \times 10^{-31} = 108x^ 5$
$9.259 \times 10^{-34} = x^ 5$
$ \sqrt [ 5] {9.259 \times 10^{-34}} = x$
$2.474 \times 10^{-7} = x$
- This is the molar solubility value for this salt.