Fractional Precipitation Pogil Answer Key

POGIL Insight: In reality, adding (Cl^-) to (Pb^2+) forms soluble complexes like (PbCl_3^-) at high ([Cl^-]). This is why in qualitative analysis, we add cold HCl specifically for (Pb^2+)—heat and excess (Cl^-) redissolve (PbCl_2).

Answer: Yes, but only within a specific window. A separation is "complete" when less than 0.1% of the first ion remains.

POGIL Answer: To separate (Ag^+) from (Pb^2+): fractional precipitation pogil answer key

Let’s assume a standard POGIL scenario: You have a solution containing 0.01 M Ag⁺, 0.01 M Pb²⁺, and 0.01 M Hg₂²⁺. You slowly add 0.1 M HCl (source of Cl⁻ ions). Relevant Ksp values:

By adding a reagent (like (Cl^-) ion) drop by drop, we can cause the ion with the smallest (K_sp) to precipitate first, leaving the other in solution. POGIL Insight: In reality, adding (Cl^-) to (Pb^2+)

Answer: Their precipitation [Cl⁻] values are very close (1.14×10⁻⁸ M vs. 1.8×10⁻⁸ M). There is significant overlap; some AgCl will begin to precipitate before all Hg₂²⁺ is removed.

Explanation: Effective separation requires the Ksp values to differ by several orders of magnitude (e.g., 10⁴ or more). Here, the ratio is ~1.6×, so co-precipitation occurs. Let’s assume a standard POGIL scenario: You have

Question: If a solution has 0.1 M (Ba^2+) and 0.1 M (Sr^2+), and you add (Na_2SO_4) ( (BaSO_4) (K_sp=1.1\times10^-10), (SrSO_4) (K_sp=3.2\times10^-7)), which precipitates first? Calculation:

Before diving into specific answer keys, let's review the three pillars of fractional precipitation.