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Sometimes, people are beautiful. Not in looks. Not in what they say. Just in who they are.

Sometimes, people are beautiful. Not in looks. Not in what they say. Just in who they are. -Markus Zusak. IT IS USEFUL WHEN WE WRITE EQUATIONS FOR REACTIONS THAT OCCUR IN AQUEOUS SOLUTION TO INDICATE IF THE REACTANTS AND PRODUCTS ARE IONS OR MOLECULES OR IONIC SOLIDS.

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Sometimes, people are beautiful. Not in looks. Not in what they say. Just in who they are.

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  1. Sometimes, people are beautiful. Not in looks. Not in what they say. Just in who they are. -Markus Zusak

  2. IT IS USEFUL WHEN WE WRITE EQUATIONS FOR REACTIONS THAT OCCUR IN AQUEOUS SOLUTION TO INDICATE IF THE REACTANTS AND PRODUCTS ARE IONS OR MOLECULES OR IONIC SOLIDS. LET’S CONSIDE THE FOLLOWING EXAMPLE: Pb(NO3)2 (aq) + 2KI (aq)  PbI2 (s) + 2KNO3 (aq) Pb(NO3)2, KI, and KNO3 ARE ALL IONIC, SO WE COULD WRITE THE EQUATION AS: Pb+2 (aq) + 2NO3- (aq) + 2K+ (aq) + 2I- (aq)  PbI2 (s) + 2K+ (aq) + 2NO3- (aq) THIS IS CALLED A COMPLETE IONIC EQUATION.

  3. IF YOU WILL NOTICE, THERE ARE CERTAIN IONS THAT ARE THE SAME ON BOTH SIDES OF THE EQUATION – NO3-, K+. THESE ARE CALLED SPECTATOR IONS. SPECTATOR IONS DO NOT PARTICIPATE IN THE REACTION, AS THEY DO NOT CHANGE FROM ONE SIDE OF THE EQUATION TO THE OTHER. WE CAN REWRITE THE EQUATION FOR THE REACTION, LEAVING THE SPECTATOR IONS OUT. THIS IS CALLED THE NET IONIC EQUATION. Pb+2 (aq) + 2I- (aq)  PbI2 (s) NOTE: IF EVERY ION IN A COMPLEX REACTION EQUATION IS A SPECTATOR ION, NO REACTION OCCURS.

  4. RULES FOR WRITING NET IONIC EQUATIONS: • WRITE A BALANCED MOLECULAR EQUATION FOR THE REACTION. • REWRITE THE EQUATION TO SHOW THE IONS THAT FORM IN SOLUTION WHERE EACH SOLUBLE STRONG ELECTROLYTE DISSOCIATES OR IONIZES INTO ITS COMPONENT IONS. ONLY STRONG ELECTROLYTES DISSOLVED IN AQUEOUS SOLUTION ARE WRITTEN IN IONIC FORM. • IDENTIFY AND CANCEL SPECTATOR IONS. • EXAMPLE: GIVEN THE BALANCED MOLECULAR EQUATION: • CaCl2 (aq) + Na2CO3 (aq)  CaCO3 (s) + 2NaCl (aq) • WRITE THE NET IONIC EQUATION.

  5. Ca+2 + 2Cl- + 2Na+ + CO3-2 == CaCO3 (s) + 2Na+ + 2Cl- GETTING RID OF SPECTATOR IONS, THE NET IONIC EQUATION IS Ca+2 + CO3-2 == CaCO3 (s) MOLECULAR IONS YOU SHOULD KNOW: OH- HYDROXIDE ION CO3-2 CARBONATE ION SO4-2 SULFATE ION NO3- NITRATE ION NH4+ AMMONIUM ION

  6. IN IONIC REACTIONS, SOLIDS THAT FORM ARE CALLED PRECIPITATES. REACTIONS THAT FORM PRECIPITATES ARE PRECIPITATION REACTIONS. REMEMBER THAT WHETHER OR NOT A SUBSTANCE IS SOLUBLE IN SOLUTION DEPENDS ON THE ENERGY REQUIRED TO SEPARATE THE IONIC SOLID INTO ITS RESPECTIVE IONS, THE ENERGY REQUIRED TO SEPARATE THE SOLVENT MOLECULES, AND THE ENERGY RELEASED WHEN THE IONS ASSOCIATE WITH THE SOLVENT MOLECULES. KNOWING WHICH IONS WILL FORM PRECIPITATES IS VERY USEFUL IN IDENTIFYING IONS IN SOLUTIION. TABLES THAT REFLECT WHICH IONS WILL FORM PRECIPITATES ARE CALLED SOLUTILITY TABLES.

  7. AS CHEMISTS, WE ARE CONCERNED ABOUT SOUBILITY. FOR EXAMPLE, TOOTH ENAMEL IS SOLUBLE IN ACIDIC SOLUTIONS. WHEN WATER FLOWS OVER CERTAIN MINERALS, THEY CAN DISSOLVE, AND, UNDER CERTAIN CIRCUMSTANCES, REPRECIPITATE. AND, FORMING INSOLUBLE PRECIPITATES IS A GOOD WAY TO SEPARATE AND PURIFY CERTAIN IONS. THERE ARE SOME GUIDELINES FOR COMMON IONIC COMPOUNDS IN WATER.

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