Question

1. Cad4u, a local metal processing facility, is currently violating its discharge permits for dissolved cadmium, Cd²⁺. The regulations are based on activity rather than concentration, and so the savvy chief chemist decides to alter the ionic strength to meet the discharge regulations. Currently the Cd²⁺ is discharged in very low ionic strength water (I <<0.001 M). Three salts are available: MgBr₂ ($5/mol), MgSO₄ ($10/mol), and NaCl ($3/mol). If the Cd²⁺ activity must be lowered by at least 40%, which salt is the most economical choice?

Answer 1