KCN is an ionic compound that dissociates itself upon its addition to the solvent to form a solution. When it is in the solution it forms ions. The balanced dissociation for for KCN is
KCN ---> K^+1 + CN^-1
The dissociation of 1 mole of KCN forms 1 mole of potassium ion (K^+) and 1 mole of cyanide (CN^-1). The equation is already balanced.