Chapter 14: Compounds in Aqueous Solutions: Dissociation: Separation of ions that occurs when an ionic compound dissolves. EX; H2O H2O NaCl (s) Na+ (aq) + Cl-(aq) CaCl2 (s) Ca2+ (aq) + 2Cl-(aq) 1 f.u. 1 f.u. 1 f.u. 1 f.u. 1 f.u. 2 f.u. 1 mole 1 mole 1 mole 1 mole 1 mole 2 mole When ionic compounds dissolve in water their ions are hydrated by water molecules as they dissociate (separate from one another). Assume 100% dissociation for all ionic compounds. Problems: 1. Write the equation for the dissolution of magnesium chlorate in water. How many moles of ions are produced for every 1 mol of magnesium chlorate dissolved? 2. Write the equation for the dissolution of NH4NO3 in water. How many moles of each type of ion are produced if 3.5 mol of NH4NO3 dissolved? How many total moles produced? 3. An aqueous solution is analyzed and found to contain potassium ions and sulfite ions. Write the equation for the dissolution of the salt that produced this solution. If the solution contains 0.50 mol of potassium ions, how many moles of sulfite ions are present? Precipitation Reactions: No ionic compound is entirely insoluble in water. Some ionic compounds are just considered insoluble because their solubility is less than 0.1 g/100g water. SOLUBILITY RULES: 1. If insoluble, dissociation equations cannot be written. 2. Useful in predicting what will happen if solutions of 2 different soluble compounds are mixed. If produces insoluble compound = double replacement reaction & precipitate (attraction between ions is greater than attraction between ions & water) Are the following soluble or insoluble? a. KCl c. AgCl e. Ca3(PO4)2 b. NaNO3 d. BaSO4 f. Pb(ClO3)2 Net ionic equations: includes only those compounds and ions that undergo a chemical change in a reaction in an aqueous solution.
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