Hint Given the following information, calculate the acid dissociation constant, Ka, for hydrogen cyanide, HCN. (CN)2(g) + 2H* (aq) + 2e¯ = 2HCN(aq) E° 0.373 V E = 0.041 V Number Previous Give Up & View Solution Check Answer Next ☑ The formal potential, E", is the reduction potential at pH = 7. Start by writing the Nernst equation for the reaction and then express the concentration of HCN in terms of the formal concentration.