Most "Fractional Precipitation" POGIL activities use a mixture of 0.01 M (AgNO_3) and 0.01 M (Pb(NO_3)_2). A solution of 0.1 M HCl is added slowly.

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:

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+):

Precipitation occurs when Q > (K_sp).

Question: Why is fractional precipitation sometimes impossible? Answer: If the (K_sp) values of the two salts are too close (within a factor of (10^2) or (10^3)), or if the second salt requires a lower anion concentration than the first, then one salt will not be completely removed before the other starts precipitating. This causes coprecipitation (both solids form together).

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:

Before diving into the POGIL answers, let’s establish the foundational chemistry.

Precipitation occurs when two soluble salts react to form an insoluble solid (the precipitate). For example, mixing silver nitrate (AgNO₃) and sodium chloride (NaCl) forms solid AgCl.

Fractional Precipitation is a technique used to separate a mixture of metal ions from a solution. It relies on a key principle: Different ions have different solubilities (Ksp values). By carefully adding a precipitation agent (like chloride, sulfide, or hydroxide ions), you can cause the least soluble compound to precipitate first, leaving the more soluble ions in solution.

The Golden Rule: The ion with the smallest Ksp (solubility product constant) will precipitate at the lowest concentration of the precipitating agent.

Fractional Precipitation Pogil Answer Key -

Most "Fractional Precipitation" POGIL activities use a mixture of 0.01 M (AgNO_3) and 0.01 M (Pb(NO_3)_2). A solution of 0.1 M HCl is added slowly.

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:

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

POGIL Answer: To separate (Ag^+) from (Pb^2+):

Precipitation occurs when Q > (K_sp).

Question: Why is fractional precipitation sometimes impossible? Answer: If the (K_sp) values of the two salts are too close (within a factor of (10^2) or (10^3)), or if the second salt requires a lower anion concentration than the first, then one salt will not be completely removed before the other starts precipitating. This causes coprecipitation (both solids form together).

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: Precipitation occurs when Q > (K_sp)

Before diving into the POGIL answers, let’s establish the foundational chemistry.

Precipitation occurs when two soluble salts react to form an insoluble solid (the precipitate). For example, mixing silver nitrate (AgNO₃) and sodium chloride (NaCl) forms solid AgCl. Let’s assume a standard POGIL scenario: You have

Fractional Precipitation is a technique used to separate a mixture of metal ions from a solution. It relies on a key principle: Different ions have different solubilities (Ksp values). By carefully adding a precipitation agent (like chloride, sulfide, or hydroxide ions), you can cause the least soluble compound to precipitate first, leaving the more soluble ions in solution.

The Golden Rule: The ion with the smallest Ksp (solubility product constant) will precipitate at the lowest concentration of the precipitating agent.