Precipitation Reactions: Real-World Examples and Applications

📚 Quick Study Guide

• 🔍 Precipitation reactions occur when two aqueous solutions mix, resulting in the formation of an insoluble solid (precipitate).
• 🧪 The general form of a precipitation reaction is: $A^+B^- (aq) + C^+D^- (aq) \rightarrow A^+D^- (aq) + C^+B^- (s)$ where $C^+B^-$ is the precipitate.
• 📝 Solubility rules determine whether a precipitate will form. Key rules include:
• 💡 All nitrates ($NO_3^−$) are soluble.
• ✨ All Group 1 metal salts (Li+, Na+, K+, etc.) and ammonium ($NH_4^+$) salts are soluble.
• 🔥 All chlorides (Cl−), bromides (Br−), and iodides (I−) are soluble except those of silver (Ag+), lead (Pb2+), and mercury (Hg2+).
• 💧 Most sulfates ($SO_4^{2−}$) are soluble except those of barium (Ba2+), strontium (Sr2+), lead (Pb2+), and calcium (Ca2+).
• ⚙️ Most hydroxides ($OH^−$) and sulfides ($S^{2−}$) are insoluble except those of Group 1 metals and ammonium.
• 💥 Most carbonates ($CO_3^{2−}$) and phosphates ($PO_4^{3−}$) are insoluble except those of Group 1 metals and ammonium.
• 🌍 Real-world applications include water treatment (removing heavy metals), qualitative analysis (identifying ions), and the creation of pigments.

🧪 Practice Quiz

1. Which of the following pairs of solutions will form a precipitate when mixed?
   1. Sodium chloride (NaCl) and potassium nitrate (KNO3)
   2. Silver nitrate (AgNO3) and sodium chloride (NaCl)
   3. Copper(II) sulfate (CuSO4) and ammonium nitrate (NH4NO3)
   4. Lithium bromide (LiBr) and calcium iodide (CaI2)
2. What is the precipitate formed when lead(II) nitrate ($Pb(NO_3)_2$) reacts with potassium iodide (KI)?
   1. Potassium nitrate ($KNO_3$)
   2. Lead(II) iodide ($PbI_2$)
   3. Lead(II) oxide (PbO)
   4. Potassium iodide (KI)
3. Which of the following compounds is insoluble in water?
   1. Sodium nitrate ($NaNO_3$)
   2. Potassium chloride (KCl)
   3. Silver chloride (AgCl)
   4. Ammonium sulfate ($(NH_4)_2SO_4$)
4. In water treatment, which of the following is commonly used to precipitate out heavy metals?
   1. Hydrochloric acid (HCl)
   2. Sodium hydroxide (NaOH)
   3. Nitric acid ($HNO_3$)
   4. Sulfuric acid ($H_2SO_4$)
5. What type of reaction is a precipitation reaction?
   1. Redox reaction
   2. Acid-base reaction
   3. Double displacement reaction
   4. Combustion reaction
6. Which of the following solutions, when mixed with copper(II) sulfate ($CuSO_4$), will NOT form a precipitate?
   1. Sodium hydroxide (NaOH)
   2. Barium chloride ($BaCl_2$)
   3. Potassium sulfide ($K_2S$)
   4. Sodium nitrate ($NaNO_3$)
7. What is the driving force behind a precipitation reaction?
   1. Formation of water
   2. Formation of a gas
   3. Formation of a soluble salt
   4. Formation of an insoluble solid