6 Under the common-ion effect, what is the hydronium ion [H] concentration in a solution prepared by mixing 0.10 M HCN with 0.050M -10 NaCN? Assume that Ka = 4.9 10 for HCN. (Note: this problem can also be solved using the H-H equation of buffers) O A.2.4 x 10-10 M OB.4.9 10-10 M X OC.98 x 10-10 M OD. 7.0 x 10-6 M