Fractional Precipitation Pogil Answer Key Best Work ✰

Calculate how much of the first ion has precipitated before the second ion begins to form a solid.

Fractional precipitation relies on the principle that the substance with the lowest solubility

Before diving into answer keys, let's recap the science. Fractional precipitation is a technique used to separate two or more ions (e.g., Cl⁻, I⁻, or Ba²⁺, Ca²⁺) from an aqueous solution. It relies on adding a precipitating reagent (like AgNO₃ or Na₂SO₄) drop by drop. The ion that forms the least soluble compound (lowest Ksp) will precipitate first.

[Cl−]=1.6×10-5 Mopen bracket Cl raised to the negative power close bracket equals 1.6 cross 10 to the negative 5 power M fractional precipitation pogil answer key best

value is a constant at a given temperature that defines the absolute limit of ion concentration a solution can hold before dropping out a solid. A lower Kspcap K sub s p end-sub

often leads to earlier precipitation, but be careful when comparing compounds with different ion ratios (e.g., a 1:1 salt vs a 2:1 salt), as the stoichiometry alters the direct comparability of Kspcap K sub s p end-sub magnitudes.

b) What is the [CO₃²⁻] required to begin precipitation of the first ion? c) When the second ion just begins to precipitate, what fraction of the first ion remains in solution? Calculate how much of the first ion has

For PbCrO₄ (1:1 salt): [ [Pb^2+] = \frac2.8 \times 10^-130.050 = 5.6 \times 10^-12 M ]

Let's apply this method to a common scenario. Imagine you have a solution that is 0.010 M in both Cl⁻ and I⁻ ions. You add AgNO₃. (Ksp for AgCl = 1.8 × 10⁻¹⁰; Ksp for AgI = 8.5 × 10⁻¹⁷)

To find the exact concentration of the added reagent required to initiate precipitation for each ion, use the standard Kspcap K sub s p end-sub expression: It relies on adding a precipitating reagent (like

[Cl−]=1.8×10-103.46×10-6=5.2×10-5 Mopen bracket Cl raised to the negative power close bracket equals the fraction with numerator 1.8 cross 10 to the negative 10 power and denominator 3.46 cross 10 to the negative 6 power end-fraction equals 5.2 cross 10 to the negative 5 power M Step 4: Evaluate Separation Efficiency

Suppose a solution contains 0.1 M Ba2+ and 0.1 M Pb2+. If sulfate ions (SO42-) are added to the solution, which ion will precipitate first?