Hydrogen cyanide is a weak acid with Ka = 4.9 x 10-10. Calculate the pH of a solution (to 2 decimal places) containing 2.28 g of Sr(CN)2 per 158 mL.

Answer 1

Sr(CN)2 ==> Sr+^2 + 2CN^-

CN^- + HOH ==> HCN + OH^-

Kb = Kw/Ka = (HCN)(OH^-)/(CN^-)

Convert 2.28 g Sr(CN)2 per 0.158L to mols/L.(Note that Sr(CN)2 has 2 CN^- per mole of Sr(CN)2.)
Plug x for (HCN) and x for (OH^-), solve for (OH^-), convert to pOH, then to pH.
Post your work if you get stuck.

Answer 2

Above posted by DrBob222.