111. Solving a chemistry problem

At 25 °C, the rate constant of a second-order reaction in solution between an anion with charge Z = –1 and an ion with an unknown charge has the following values at two ionic strengths: 1.763×10–3 dm3/(mol•s) at I = 0.01 mol/ dm3 and 1.40×10–3 dm3/(mol·s) at I = 0.0025 mol/dm3. Determine the charge of the second ion and the rate constant at zero ionic strength. (The charge should be rounded to the nearest whole number).