Construct a rough plot of pH versus volume of added base for the titration of 50 mL of 0.055 M HCN with 0.075 M NaOH. Ka = 4.0*10-10 for HCN Figure 17.11. (a) What is the pH before any NaOH is added? (b) What volume of base, in milliliters, is required to reach the equivalence point? (c) What is the pH at the equivalence point? (d) What indicator would be most suitable to determine the endpoint? Bromthymol blue Alizarin yellow GG bromcresol purple bromocresol green