Pogil Answer Key: Fractional Precipitation
Hg₂Cl₂ and possibly some AgCl precipitate, but PbCl₂ remains dissolved.
POGIL worksheets guide you to calculate the exact concentration of the added ion needed to initiate precipitation. This relies heavily on the Reaction Quotient ( Kspcap K sub s p end-sub relationship: Precipitation begins the exact moment
The solubility decreases from 1.34 × 10⁻⁵ M to 1.8 × 10⁻¹⁰ M—a reduction by a factor of approximately 75,000.
Precipitation occurs when .
A solution is 0.01 M (Fe^3+) and 0.01 M (Cu^2+). (K_sp) (Fe(OH)_3 = 4\times10^-38), (Cu(OH)_2 = 2.2\times10^-20).
Remember: Chemistry is not about memorizing outcomes but about predicting them. The next time you see an unknown mixture of cations, you will know exactly which reagent to add and in what order to pull them apart.
Hg₂Cl₂ has the smallest Ksp (1.3 × 10⁻¹⁸), so it will precipitate first. fractional precipitation pogil answer key
Ksp=[Ag+][I−]cap K sub s p end-sub equals open bracket cap A g raised to the positive power close bracket open bracket cap I raised to the negative power close bracket
Fractional precipitation is the sequential removal of ions from a solution by adding a specific precipitating agent.
Always calculate the required precipitant concentration . For (Ag_2S) (very small (K_sp)) vs. (CuS), the sulfide ion needed might be different due to stoichiometry. Hg₂Cl₂ and possibly some AgCl precipitate, but PbCl₂
of its original value) before the second ion starts precipitating, the separation is deemed effective. 3. Common Pitfalls Identified in the Answer Key
A typical POGIL on fractional precipitation presents you with:
In many versions of this POGIL, the initial model explores separating Zn2+cap Z n raised to the 2 plus power Cu2+cap C u raised to the 2 plus power ions using sodium carbonate ( Na2CO3cap N a sub 2 cap C cap O sub 3 : Solution A : Contains Zinc Nitrate and Copper(II) Nitrate. Solution B : Sodium Carbonate ( Na2CO3cap N a sub 2 cap C cap O sub 3 ), which provides the CO32−cap C cap O sub 3 raised to the 2 minus power ions needed for precipitation. Precipitation occurs when
AgCl(s)⇌Ag+(aq)+Cl−(aq)AgCl open paren s close paren is in equilibrium with Ag raised to the positive power open paren a q close paren plus Cl raised to the negative power open paren a q close paren
While exact questions vary across different versions of POGIL worksheets, they generally follow a structured sequence of inquiry. Below is the step-by-step logic required to solve these problems. Phase 1: Identifying the Order of Precipitation