Reactions in Aqueous Solutions Study Guide 4 PDF

Investigation 4 Experience 5 Reactions in Aqueous Solutions  OBJECTIVE Students will understand how ions are formed, and reactions take place in water.  New Vocabulary aqueous solution solute solvent complete ionic equation  Review Vocabulary solutio...

Investigation 4 Experience 5 Reactions in Aqueous Solutions  OBJECTIVE Students will understand how ions are formed, and reactions take place in water.  New Vocabulary aqueous solution solute solvent complete ionic equation  Review Vocabulary solution: a uniform mixture that might contain solids, liquids, or gases  Aqueous Solutions When a substance dissolves in water, a solution forms. An aqueous solution contains one or more substances called solutes dissolved in the water. Water is the solvent—the most plentiful substance in the solution.  Aqueous Solutions Molecular Compounds in Solution There are many possible solutes. Sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions. Other solutes are molecular compounds that form ions when they dissolve in water. Compounds that produce hydrogen ions in aqueous solutions are acids.  Aqueous Solutions Ionic compounds can also be solutes in aqueous solutions. When ionic compounds dissolve in water, their ions separate in a process called dissociation.  Polar and Non-polar Nonpolar compounds typically do not dissolve in water. You may know that oil and water do not mix. Oils are made up of large, mostly nonpolar molecules. Because oil is generally nonpolar and does not form ions, it is not solvated by polar water molecules and so does not dissolve in water. Nonpolar compounds tend to dissolve only in other nonpolar compounds.  Polar and Non-polar As oil is non-polar, there are certain salts which are soluble and insoluble in water. If the salt is soluble in water, it breaks to form ions in aqueous solution. If the salt is insoluble in water, it will form a precipitate. Soluble salts Insoluble salts NaCl (Sodium Chloride) Cu(OH)2 (Copper hydroxide) CuSO4 (Copper(II) Sulphate) BaSO4 (Barium Sulphate) Na2CO3 (Sodium Carbonate) BaCO3 (Barium Carbonate)  Review Polyatomic Ions Name Ion hydroxide OH- carbonate CO32- nitrate NO3- sulphate SO42- All Group 1 +1 e.g. Na+ All Group 2 +2 e.g. Ca2+ All Group 6 -2 e.g. O2- All Group 7 -1 e.g. Cl-  Types of Reactions in Aqueous Solutions When two aqueous solutions that contain ions as solutes are combined, the ions might react with one another. These reactions are always double- replacement reactions. The solvent molecules, which are all water molecules, do not usually react. Spectator ions are ions present in water but do not take part in chemical reaction.  Types of Reactions in Aqueous Solutions Reactions that form water Another type of double-replacement reaction that occurs in an aqueous solution produces water molecules. For example: HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq) H+(aq) + Br-(aq) + Na+(aq) + OH-(aq) → H2O(l) + Na+(aq) + Br-(aq) Similar ions on reactant and product side are cancelled. Spectator ions: Na+ and Br- Without spectator ions, the reaction looks like this: H+(aq) + OH–(aq) → H2O(l)  Types of Reactions in Aqueous Solutions Reactions that form water Reaction between an acid and alkali form salt and water. It is also a double displacement reaction. HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq) Without spectator ions, the reaction looks like this: H+(aq) + OH–(aq) → H2O(l)