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Explore solubility rules and precipitation reactions in aqueous solutions. Discover how to predict solubility and identify precipitates in chemical reactions using net ionic equations.
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Solubility Rules and Precipitation Reactions Chapter 7: Reactions in Aqueous Solutions!
Not all ionic compounds dissolve! Instead of doing experiments all the time to see which ones will dissolve, we use The solubility rules.
Solubility Rules • All nitrates (NO3-) are soluble. • All ammonium (NH4+) or alkali (Li+, Na+, K+, Rb+, Cs+, Fr+) compounds are soluble. • All carbonates (CO32-), phosphates (PO4 3-) and hydroxides (OH-) are insoluble except with the cations in Rule #2. 4. All chlorides (Cl-), bromides (Br-), and iodides (I-), are soluble except with Ag+, Pb2+, or Hg+. 5. All sulphates (SO42-) are soluble except with Ca2+, Sr2+, Ba2+, Ra2+, Pb2+,
Solubility Rules Con’t • 6. All acetates (CH3COO) are soluble except Fe3+ • 7. Except for rule 1 and 2, carbonates, oxalates, sulfites, chromates, oxides, silicates, and phosphates are insoluble. • 8. Except for rule 1 and 2, Sulfides are insoluble except for calcium, barium, strontium, magnesium.
Not soluble soluble Which of the following are soluble in water? • SrSO4 • NaNO3 • PbCl2 Not soluble
Precipitation Reactions When a solid doesn’t dissolve it is called insoluble. A solid that forms when two solutions are mixed is called a precipitate. Remember!!! State of matter is shown as a subscript in parentheses after the element or compound Solid (s) Aqueous/dissolved (aq) Gas (g)
Predict the products of the following reaction: (if no solid precipitate is formed, there is no reaction) Pb(NO3)2(aq) + KI (aq) Pb(NO3)2(aq) + 2KI (aq) PbI2(s) + 2KNO3 (aq) We know it is a solid precipitate because it is insoluble according to the solubility rules.
A picture of the reaction: Because K+ and NO3- remain dissolved, they are called spectator ions and are not included in the net ionic equation. Net Ionic Equation Pb2+ (aq) + 2I-(aq) PbI2(s) NO3- NO3- Pb2+ K+ I- K+ NO3- PbI2(s)
Net Ionic Equation Write the balanced chemical and net ionic equation for: Na2CO3(aq) + CaCl2(aq) Step 1: Write the balanced chemical equation Na2CO3(aq) + CaCl2(aq) CaCO3(s) + 2NaCl (aq) Step 2: Remove the spectator ions (those that are soluble). Ca2+(aq) + CO32-(aq) CaCO3(s) Insoluble precipitate