Question

Zinc is to be used as an internal standard for the polarographic analysis of thallium. A standard solution containing twice the concentration of zinc as thallium has diffusion currents of 1.89 microAmps for thallium and 3.5 microAmps for zinc. A 10.0g sample of an alloy containing thallium but no zinc is dissolved to make 500ml of solution. To 25ml of this solution is added 25ml of a 0.001M zinc solution. The diffusion currents are then measure and found to be 18.2 microAmps for Tl and 14.5 microAmps for Zn. Calculate percentate of thallium in d alloy