So if I am trying to find the concentration of all species present (Na+, C6H5CO2-, C6H5CO2H, H3O+, and OH-) in a solution of 0.042M sodium benzoate (C6H5CO2Na) and I know that Ka for benzoic acid is 6.5*10^-5, then do I just take Kw/Ka=Kb and then set Kb=x^3/0.042 to find the concentrations of Na+, C6H5CO2H, and OH- (which I get to be 1.8*10^-4)? And then to find both H3O+ and C6H5CO2- do I just take Kw/(1.8*10^-4)?
By the way, I get the reaction equation to be C6H5CO2Na + H2O --> Na+ + C6H5COH + OH-