) precipitates first. Once the first ion is mostly removed, the second compound begins to precipitate. Key Chemical Principles Solubility Product Constant ( Kspcap K sub s p end-sub
Example A — 1:1 salts (e.g., AgCl and PbCl2 simplified to 1:1 for pattern)
[Ag+]=1.8×10-9 Mopen bracket cap A g raised to the positive power close bracket equals 1.8 cross 10 to the negative 9 power M Step 3: Analyze the Results AgIcap A g cap I begins to precipitate when AgClcap A g cap C l will not start precipitating until is increased to . This gap allows for effective separation. 4. Why Copying the Answer Key Limits Your Success fractional precipitation pogil answer key
Step 2 — Compute critical precipitant concentration for each cation:
Step 5 — Completing calculations:
Identify the two potential precipitates and write their dissociation equations and Kspcap K sub s p end-sub expressions.
Imagine you have a solution containing two halide ions—chloride (Cl⁻) and iodide (I⁻). If you slowly add silver nitrate (AgNO₃), which compound will precipitate first: AgCl or AgI? The Ksp of AgCl is around 1.8 × 10⁻¹⁰, and the Ksp of AgI is significantly smaller, at about 8.5 × 10⁻¹⁷. Because it is much less soluble, AgI will be the first solid to appear. This difference in solubility allows for the separation of the two ions. ) precipitates first
[Ag+]required for Ag2CrO4=Ksp(Ag2CrO4)[CrO42−]open bracket Ag raised to the positive power close bracket sub required for Ag sub 2 CrO sub 4 end-sub equals the square root of the fraction with numerator cap K sub s p end-sub open paren Ag sub 2 CrO sub 4 close paren and denominator open bracket CrO sub 4 raised to the 2 minus power close bracket end-fraction end-root Step 3: Identify the First Precipitate Compare the two calculated values for
To find the exact concentration needed to start precipitation, set and solve for For : This gap allows for effective separation