V mL of 0.4 M Pb(NO ₃)₂ solution is mixed with 100 mL of 0.2 M KI solution. If the final concentration of nitrate ions in the resulting mixture is 0.4 M, what is the final concentration of Pb ²⁺ ions in the solution?

Step-by-step solution

First, we determine the volume V using the concentration of the spectator ion, NO ₃^- . Millimoles of NO ₃^- initially present = V 0.4 2 = 0.8V Total volume of the mixture = (V + 100) mL Final concentration of NO ₃^- = 0.8V V + 100 = 0.4 0.8V = 0.4V + 40 0.4V = 40 V = 100 mL Now, calculate the initial millimoles of the reacting ions: Millimoles of Pb ²⁺ = 100 0.4 = 40 mmol Millimoles of I ^- = 100 0.2 = 20 mmol The precipitation reaction is: Pb ²⁺ + 2 I ^- PbI ₂(s) From the stoichiometry, 1 mole of Pb ²⁺ reacts wit