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Solutions where water is the solvent ◦ Chemical is dissolved in water Water is the “universal solvent” ◦ O-H bonds are covalent, e- not shared equally ◦ Oxygen has a slight negative, hydrogen slight positive Polar molecule Oxygen has a strong attraction to cations, hydrogen to anions Molecules “fall apart” or dissolve when surrounded by water molecules Once dissolved, ions exist separately Solution contains both cation and anion Solubility (dissolve-ability) of substances varies greatly Nonpolar molecules (fats, oils) do not dissolve in water “Like dissolves like” Solutions with a large number of ions present in solution are excellent conductors of electricity ◦ Completely ionized ◦ Strong electrolyte Strong acids (HCl, H2SO4), strong bases (NaOH, KOH), salts (NaCl, KBr) Weak conductors have only a few ions present in solution ◦ Partially ionized ◦ Weak electrolyte Weak acids (HF, HC2H3O2), weak bases (NH3) Show the amount of ionization occurring ◦ Example: Magnesium chloride dissolving in water MgCl2(s) Mg2+(aq) + 2 Cl-(aq) ◦ Positive ends of water surround the chlorine, negative ends surround magnesium Ions are hydrated Strong electrolyte Acetic acid in water HC2H3O2(aq) H+(aq) + C2H3O2-(aq) Partially dissociates ◦ Weak electrolyte Ethanol in water C2H5OH(aq) No ionization No ionization ◦ No ions in solution ◦ Non electrolyte – sugars, alcohols Molarity (M) = mol of solute L of solution 3 M KOH: 3 mol of KOH 1 L of solution Concentration of ions in solution can be calculated MgCl2(s) Mg2+(aq) + 2 Cl-(aq) If MgCl2 is 0.2 M, what is concentration of Mg2+? Of Cl-? Concentration of Mg2+is 0.2 M and Cl- is 0.4 M ◦ 1:1 ratio of MgCl2 : Mg2+ ◦ 1:2 ratio of MgCl2 : Cl- Square brackets are used to denote concentration [MgCl2] = 0.2 M Calculate the number of moles of Cl- in 1.75 L of 1.0 x 10-3 M ZnCl2 water ZnCl2 Zn+ + 2 Cl- Solutions are often more concentrated than you need. M1V1 = M2V2 What volume of 16 M sulfuric acid must be used to prepare 1.0 L of a 0.20 M H2SO4 solution ? Occurs when certain cations and anions join to form insoluble compounds ◦ Compounds don’t dissolve in water ◦ Form (insoluble) solids – precipitates Ionic compound bonded so strongly, water can’t pull it apart We need to know solubility rules! ◦ Sadly, lots of memorization ◦ Thankfully, your teacher gave you a handy chart An “easy” way to think about them Always Soluble Except With NH4+, NO3-, ClO3-, ClO4-, C2H3O2No exceptions! and IA metals Cl-, Br-, I- Ag+, Hg2+ and Pb2+ SO42- Ca2+, Sr2+ Ba2+, Ag+, Hg2+ and Pb2+ F- IIA Metals Based on solubility rules, we can predict what will happen in reactions Will a precipitate form when solutions of silver nitrate and lithium bromide are mixed? AgNO3(aq) + LiBr(aq) AgBr(?) + LiNO3(?) Is Br- soluble with Ag+? Is NO3- soluble with Li+? AgNO3(aq) + LiBr(aq) AgBr(s) + LiNO3(aq) ◦ Nitrate – ALWAYS, IA – ALWAYS ◦ Br- - sometimes, but not with Ag+ If there is no precipitate, the reaction does not occur Ions would all still be in solution Ions switch partners Mix together solutions of MgCl2 and AgNO3 MgCl2(aq) + 2 AgNO3(aq) Mg(NO3)2(?) + 2 AgCl(?) Is Mg(NO3)2 soluble? Is AgCl? MgCl2(aq) + 2 AgNO3(aq) Mg(NO3)2(aq) + 2 AgCl(s) Can calculate the mass or concentration of ions/precipitate is formed. AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) If 0.275 L of .100 M AgNO3 is mixed with 0.135 L of 1.00 M NaCl, how many grams of AgCl would be formed? Find moles of each reactant to find limiting reactant Find out how many moles of solid AgCl forms Convert to grams