How do you calculate the pH at the equivalence point for the titration of 0.140 M methylamine (CH_3NH_2) with 0.140 M HCI? The K_b of methylamine is 5.0x10^-4?
at the equivalent point you have CH_3NH_3Cl, and having unitet the two solutions you have a concentration of 0,07 M, The pH is given by [OH^-]=sqrt(Cs(Kw)/(Ka)) =sqrt (0,07 xx 10^(-14)/(5 xx 10^(-5))) = 3,7 xx 10^(-6)
pOH= 5.43; pH = 8,57