Chapter09_Fall11

Chapter09_Fall11 - 9 9.1 9.2 9.3 9.4 9.5 9.6 Reactions in...

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11/10/2011 1 Reactions in Aqueous Solutions 9 9.1 Electrolytes and Nonelectrolytes 9.2 Precipitation Reactions 9.3 Acid-Base Reactions 9.4 Oxidation-Reduction Reactions 9.5 Concentration of Solutions 9.6 Aqueous Reactions and Chemical Analysis General Properties of Aqueous Solutions A solution is a homogenous mixture of two or more substances. The substance present in the largest amount (moles) is referred to as the solvent . The other substances present are called the solutes . Electrolytes and Nonelectrolytes An electrolyte is a substance that dissolves in water to yield a solution that conducts electricity NaCl( s ) Na + ( aq ) + Cl ( aq ) An electrolyte undergoes dissociation and breaks apart into its constituent ions.
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11/10/2011 2 Electrolytes and Nonelectrolytes A nonelectrolyte is a substance that dissolves in water to yield a solution that does not conduct electricity. C 12 H 22 O 11 ( s ) C 12 H 22 O ( aq ) The sucrose molecules remain intact upon dissolving. Strong and Weak Electrolytes An electrolyte that dissociates completely is known as a strong electrolyte . Strong Bases HCl(g) H+(aq) + Cl–(aq) NaOH(s) Na+(aq) + OH–(aq) NaCl( s ) Na + ( aq ) + Cl ( aq ) Water soluble ionic compounds Strong Acids Strong Electrolytes and Weak Electrolytes A weak electrolyte is a compound that produces ions upon dissolving but exists in solution predominantly as molecules that are not ionized. CH 3 COOH( l ) H + ( aq ) + CH 3 COO - ( aq ) NH 3 ( g ) + H 2 O( l ) NH 4 + ( aq ) + OH ( aq ) Weak Acids Weak Bases Strong Electrolytes and Weak Electrolytes The double arrow, , denotes a reaction that occurs in both directions. When both the forward and reverse reactions occur at the same rate, the reaction is in a state of dynamic chemical equilibrium .
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11/10/2011 3 Classifying Chemical Reactions Chemical reactions classified by nature of the chemical process Chemical reactions classified by nature of the chemical equation Chemical Reactions Synthesis (combination) Decomposition Displacement (single/double) Chemical Reactions Precipitation Acid-base Gas evolution Oxidation- Reductions Combustion Precipitation Reactions The insoluble product that separates from a solution is called precipitate . A chemical reaction in which a precipitate forms is called a precipitation reaction. 2KI( aq ) + Pb(NO 3 ) 2 ( aq ) PbI 2 ( s ) + 2KNO 3 ( aq ) Precipitation Reactions Water is a good solvent for ionic compounds because it is a polar molecule. The polarity of water results from electron distributions within the molecule. The oxygen atom has an attraction for the hydrogen atoms’ electrons and is therefore partially negative compared to hydrogen. The oxygen atom is partially negative The hydrogen atoms are partially positive Precipitation Reactions Hydration occurs when water molecules remove the individual ions from an ionic solid surrounding them so the substances dissolves.
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11/10/2011 4 Solubility Rules Empirical Rules - deduced by observations Soluble Exception Insoluble Li + , Na + , K + , NH 4 + none NO 3 - , C 2 H 3 O 2 - none Cl - , Br - , I - Ag + , Hg 2 2+ , Pb 2+ SO 4 2- Ca 2+ , Sr 2+ , Ba 2+ , Pb
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This note was uploaded on 02/20/2012 for the course 160 161 taught by Professor Kim during the Fall '08 term at Rutgers.

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Chapter09_Fall11 - 9 9.1 9.2 9.3 9.4 9.5 9.6 Reactions in...

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