Among the following plots, which plot will be obtained for a conductometric titration of an equimolar mixture of HCl and HCN with NaOH(aq) solution?
1) pH vs. volume of NaOH(aq) solution
2) pH vs. volume of HCl
3) pH vs. volume of HCN
4) pH vs. volume of NaOH(aq) solution added to the mixture