The salts X(NO₃)₂and Y(NO₃)₂ (where X⁺ and Y⁺ are metal ions) are dissolved in water to give a solution which is 0.1 M in each of them. Using the K_sp values listed below, decide which aqueous reagent, if any, will definitely precipitate X⁺ before precipitating Y⁺ from solution. Given K_spvalues: XCl₂, 1 × 10^-5YCl₂, 1 × 10^-10X(OH)₂, 1 × 10^-10Y(OH)₂, 1 × 10^-5 A) 1 M NaCl B) 1 M HCl C) 1 M HNO₃ D) 1 M NaOH E) None of the above reagents will accomplish the precipitation.

Question

Quizplus · Accepted Answer

To determine which reagent will precipitate X before Y, we need to compare the Ksp values of the possible precipitates. The smaller the Ksp value, the less soluble the compound and the more likely it will precipitate first. 
Using the given Ksp values: 
- Ksp for XCl2 is 1 × 10^−5 
- Ksp for YCl2 is 1 × 10^−10 
- Ksp for X(OH)2 is 1 × 10^−10 
- Ksp for Y(OH)2 is 1 × 10^−5

Comparing the Ksp values, we can see that X will precipitate before Y if we add a strong base that will deprotonate X(OH)2 and drive its Ksp value down. The only option in the given reagents that fits this criteria is 1 M NaOH, which will deprotonate X(OH)2 to form the insoluble X(OH)2 precipitate before Y(OH)2 precipitates. Therefore, the answer is D.

The Salts X(NO3)2 and Y(NO3)2 (Where X+ and Y+ Are

The Salts X(NO₃)₂and Y(NO₃)₂ (Where X⁺ and Y⁺ Are