Chemical equilibrium

Exercise 16

Give the definition of $K_s$ for the saturated solution resulting from the equilibrium (don't write (aq) ): $Ag_3PO_4(s)$ $3Ag^+(aq)$ $+$ $PO_4^{3-}(aq)$ $Ca_3(PO_4)_2(s)$ $3Ca^{2+}(aq)$ $+$ $2PO_4^{3-}(aq)$ $CaF_2(s)$ $Ca^{2+}(aq)$ $+$ $2F^-(aq)$ $Al_2S_3(s)$ $2Al^{3+}(aq)$ $+$ $3S^{2-}(aq)$

$K_s$ $=$ $[Ag^+]^3[PO_4^{3-}]$ $K_s$ $=$ $[Ca^{2+}]^3[PO_4^{3-}]^2$ $K_s$ $=$ $[Ca^{2+}][F^-]^2$ $K_s$ $=$ $[Al^{3+}]^2[S^{2-}]^3$