JEE Main Chemistry question
The Ksp of PbCO₃ and MgCO₃ are 1.5×10⁻¹⁵ and 1×10⁻¹⁵ respectively at 298 K. The concentration of Pb²⁺ ions in a saturated solution containing MgCO₃ and PbCO₃ is:
Answer: (C)
Solution
Total [CO₃²⁻]≈√Ksp(PbCO₃)+√Ksp(MgCO₃)=3.87×10⁻⁸+3.16×10⁻⁸=7.03×10⁻⁸ M; [Pb²⁺]=Ksp(PbCO₃)/[CO₃²⁻]=1.5×10⁻¹⁵/7.03×10⁻⁸≈2.1×10⁻⁸ M.