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Drill – 4/8/08. 1. What is an electrolyte? 2. Is a precipitate soluble or insoluble?. Ions in Aqueous Solution Chapter 13, Section 1. Dissociation. The separation of ions that occurs when an ionic compound dissolves. NaCl ( s ) ïƒ Na + ( aq ) + Cl - ( aq )
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Drill – 4/8/08 1. What is an electrolyte? 2. Is a precipitate soluble or insoluble?
Dissociation • The separation of ions that occurs when an ionic compound dissolves. • NaCl (s) Na+ (aq) + Cl- (aq) • CaCl2 (s) Ca+2 (aq) + 2Cl- (aq) H2O H2O
H2O • NaCl (s) Na+ (aq) + Cl- (aq) • 1 mol 1 mol 1 mol • CaCl2 (s) Ca+2 (aq) + 2Cl- (aq) • 1 mol 1 mol 2 mol • Al2(SO4)3 (s) 2Al3+ (aq) + 3SO42- (aq) • 1 mol 2 mol 3 mol H2O H2O
Solubility Guidelines – Use these to determine if an ionic compound is soluble • Na+, K+, and NH4+ compounds are soluble in H2O2 • Nitrates, acetates, and chlorates are soluble. • Chlorides are soluble, except those with Ag+, Hg+, and lead. • Most sulfates are soluble, except those with Ba2+, Sr2+, Pb2+, Ca2+, and Hg+
Solubility Guidelines – Use these to determine if an ionic compound is soluble 5. Most carbonates, phosphates, and silicates are insoluble, except those of Na+, K+, and NH4+ 6. Most sulfides are insoluble, except those of Sr2+, Ca2+, Na+ , K+, and NH4+
Is calcium phosphate soluble or insoluble? • Ca3(PO4)2 • Most carbonates, phosphates, and silicates are insoluble, except those of Na+, K+, and NH4+
We can use this information to predict states of matter. We can determine if a product is either soluble (aq) or insoluble (s).
Net Ionic Equations • Include only those compounds and ions that undergo a chemical change in a reaction in aqueous solution.
How to write net ionic equations 1. Write the chemical equation. 2. Write the state of matter, making sure to identify precipitates (use solubility rules). 3. Convert chemical equations to ionic equations (do not dissociate precipitates). 3. Cancel spectator ions from both sides of the equation. Spectator ions do not take part in the chemical reaction and are found in solution both before and after the reaction.
CdSO4 and H2S • CdSO4 + H2S CdS + H2SO4 • CdSO4 (aq) + H2S (aq) CdS (s) + H2SO4 (aq) • Cd2+(aq) + SO42-(aq) + 2H+(aq) + S2-(aq) CdS(s) + SO42-(aq) + 2H+(aq) • Cd2+(aq) + S2-(aq) CdS(s)
Practice Problems • Pg. 586 in Blue Chemistry Book # 30, 41, 44, 45