Determine  [Zn2+] [CN-] [HCN] in a saturated solution of Zn(CN)2 with a fixed pH of  2.390.  The Ksp for Zn(CN)2 is 3.0x10^-16.  The Ka for HCN is  6.2x10^-10.
 Equation: Zn(CN)2(s)-> Zn2+(aq) + 2CN(aq)
 a) Write pertinent reactions
 b) Write charge balance equations
 c)Write mass balance equations
 d)Write the equilibrium constant expression for each reaction
 e)Count the equations and unknowns
 f)Solve for unknowns