011. Solving a chemistry problem

7. A 2.157 g sample of silver alloy was dissolved and, after appropriate treatment, the volume of the solution was increased to 100.0 ml. Determine the mass fraction (%) of silver in the alloy if, when titrating 25.00 ml of the prepared solution with 0.1200 M sodium chloride solution, you get:

Vt, ml 16.00 18.00 19.00 19.50 19.90 20.00 20.10 20.50 21.00
E, mV 689 670 652 634 594 518 440 401 383

Write the titration reaction equation, half-reaction and Nernst equations for the indicator electrode.