======Solubility Rules======


<WRAP right box>
**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
\\
**Categories:** {{$demo.categories}}
\\


**Alternative titles:** Precipitation Reactions, Solubility Table
</WRAP>

====Summary====                   
{{$demo.summary}}



====Procedure====  
  - Prepare an 8×12 well plate or test tubes and label columns for cations (as nitrate solutions) and rows for anions (as sodium salts).  
  - Dispense about three drops of each cation into its column wells and three drops of each anion into its row wells, creating all pairwise combinations without letting droppers touch solutions.  
  - Observe each mixture for evidence of precipitation (cloudiness, solid, color, gel-like texture) and record Y (precipitate) or N (no precipitate) in a grid; add brief notes on appearance.  
  - For wells that form a precipitate, deduce and write the formula of the insoluble compound by balancing ionic charges (total positive charge equals total negative charge).  
  - Write a net ionic equation for several representative precipitating pairs (e.g., Pb²⁺ + 2 I⁻ → PbI₂(s)).  
  - If a result is unclear in the plate, repeat that pair in a clean small test tube to confirm.  
  - Extension (Part B): Specifically test I⁻ with Ag⁺ and I⁻ with Pb²⁺ in clean wells to explore known exceptions.  
  - Develop a set of solubility rules from your grid (e.g., “all nitrates soluble,” “most carbonates insoluble except with group 1 and ammonium,” etc.).  
  - Collect all liquids in a labeled waste beaker, then transfer to the designated waste container. Rinse the plate and test tubes and return equipment.




====Links====

📄 Solubility Rules - NC State University Chemistry Department: [[https://www.webassign.net/question_assets/ncsugenchem102labv1/lab_3/manual.html]]\\


====Variations====
  * Compare results using different anion sets (e.g., acetate, chloride, bromide) to expand your rule set.  
  * Investigate concentration effects by repeating one cation–anion pair at two different molarities.  
  * Explore temperature effects on borderline precipitates by gently warming or cooling matched samples (record any reversals or increased turbidity).  
  * Use a smartphone light and dark background to improve detection of slight cloudiness; compare inter-rater judgments for reliability.



====Safety Precautions====
  * Wear gloves, and a lab coat; avoid ingestion and skin contact with all solutions, especially silver nitrate and lead(II) nitrate (toxic if ingested).  
  * Silver nitrate can stain skin dark after ~24 hours; stains fade but avoid contact.  
  * Do not cross-contaminate reagent bottles - keep droppers out of wells.  
  * Work with small volumes only; clean spills immediately with water and towels, then wash hands.  
  * Collect all liquid wastes (including rinses) in the heavy-metal/aqueous waste container as directed.





====Questions to Consider====
  * Which ions were always soluble in your grid? (Group 1 cations and ammonium; nitrate.)  
  * Which anions were usually insoluble, and with what exceptions? (Carbonate and phosphate are generally insoluble except with group 1 and ammonium.)  
  * What was the general trend for sulfate salts? (Often soluble; notable insoluble exceptions include PbSO₄, BaSO₄, and frequently SrSO₄.)  
  * What halide exceptions did you observe? (Ag⁺ and Pb²⁺ commonly form insoluble halides such as AgCl and PbI₂.)  
  * How do ion charges relate to precipitation likelihood? (Higher charge magnitude increases lattice energy, favoring precipitation.)  
  * In your observations, which rule takes precedence when rules seem to conflict—group 1/ammonium or anion insolubility? (Group 1 and ammonium solubility generally overrides anion insolubility.)  
  * Write the net ionic equation for a magnesium precipitate you observed. (Example: Mg²⁺(aq) + CO₃²⁻(aq) → MgCO₃(s), if that pair precipitated in your data.)  
  * Why are nitrate salts used as cation sources and sodium salts as anion sources? (Both nitrate and sodium/ammonium salts are typically soluble, ensuring the reacting ions are available in solution.)  
  * What is the role of spectator ions in your total ionic equations? (They remain unchanged and are omitted from the net ionic equation.)  
  * How could you reduce uncertainty in borderline cases? (Replicate trials, use clearer backgrounds, allow more settling time, or confirm in a test tube.)