chapter 4 chem notes

chapter 4 chem notes - Chapter 4:Types of Chemical...

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Chapter 4:Types of Chemical Reactions A. Dissolution Reactions B. Precipitation Reactions Solution (A homogeneous mixture of different substances) Aqueous Solution Non-aqueous solution (Water is used as solvent) ( Solvent other than water ) Solvent: Component which is in larger amount Solute: component which is in smaller amount water sugar Aqueous solution of sugar with water as solvent sugar as solute Dissolution is the process where one substance disperses into another at molecular or atomic level. The solid structure is broken and individual molecules or ions are dispersed .
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Dissolution When ionic compounds are dissolved in water, each ion is surrounded by water molecules due to ion-dipole interactions. NaCl( s ) Na + ( aq ) + Cl - ( aq ) H 2 O Ions are said to be aquated or solvated. When polar molecular (covalent) compounds are dissolved in water, the molecules of compound stay intact (do not break up) but are surrounded by water molecules due to dipole-dipole or hydrogen bonding interactions. C 6 H 12 O 6 ( s ) C 6 H 12 O 6 ( aq ) H 2 O ( aq ) indicates dissolution in water (or aqueous solution ) The molecular compound is said to be aquated or solvated .
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Electrolyte solutions (A solution that conducts current more than the solvent) Non- or weak electrolyte solutions: Addition of a substance to solvent does not increase, or slightly increases, the conductance Solutions Strong electrolyte :If a compound, upon addition to solvent, dissociates completely into constituent ions then that substance is a strong electrolyte. Example: NaCl(s) Na + ( aq ) + Cl - ( aq ) water sodium ions solvated by water molecules chloride ions solvated by water molecules Ion-ion interactions in solid NaCl are broken up in water and replaced by ion-water interactions O H H Na + O H H Cl - O H H Ionic compounds (made up of Group I and II elements) are strong electrolytes K 2 SO 4 (s) 2K + ( aq ) + SO 4 2- ( aq ) water Na + Cl - water
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Weak electrolytes : If a compound does not dissociate completely into ions then most of the ions of that compound are not dispersed into solution. Example: lead acetate, Pb(CH COO) ; Cadmium iodide, CdI Non-electrolytes : Substances that do not form any ions in solution Example: sugar solution Covalent compounds do not form ions in solution Solubility : of a substance is the largest amount of substance that will dissolve in a given amount of solvent (expressed as grams/Liter) Soluble: >10g/L; slighlty soluble : 0.1g/L-10g/L ; Insoluble: <0.1g/L (these ranges are approximate estimates meant to give guidance) Warning : When a substance is soluble that does not mean that the substance dissociates into ions!!
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(e). Most chlorides(Cl ), bromides (Br ) and iodides (I ) are soluble Slightly soluble Insoluble PbCl 2 AgCl, Hg 2 Cl 2 PbBr 2 AgBr,Hg 2 Br 2 HgBr 2 AgI,Hg 2 I 2 ,PbI 2 ,HgI 2 (f). Most sulfates, SO 4 2- , are soluble in water Slightly soluble Insoluble CaSO 4 PbSO 4 Ag 2 SO 4 SrSO 4 (a). All nitrates (NO ) are soluble in water (b). All acetates (CH
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This note was uploaded on 04/13/2008 for the course CHEM 102a taught by Professor Hanusa during the Fall '06 term at Vanderbilt.

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chapter 4 chem notes - Chapter 4:Types of Chemical...

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