[kgor93]

What is the S2- concentration in a saturated solution (0.10 M) of H2S, in which the pH has been adjusted to 6.00 by the addition of HCl?  For H2S, Ka1 = 1.1 x 10-7 and Ka2 = 1.0 x 10-14.

      a)   1.1 x 10-16M                d)   3.2 x 10-8M

      b)   1.1 x 10-10M                e)   3.2 x 10-6M

      c)   1.0 x 10-2M

Need help. Not sure how to do this.

 

[magician4]

hint:

- write an expression for K_a1 * K_a2

- remember: c₀ [itex]\approx [/itex] c for weak acids


regards

Ingo