chapt04_lec

chapt04_lec - 4-1Dr. Wolfs CHM 101Chapter 4The Major...

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Unformatted text preview: 4-1Dr. Wolfs CHM 101Chapter 4The Major Classes of Chemical Reactions4-2Dr. Wolfs CHM 101The Major Classes of Chemical Reactions4.6Elemental Substances in Redox Reactions4.1The Role of Water as a Solvent4.2Writing Equations for Aqueous Ionic Reactions4.3Precipitation Reactions4.4Acid-Base Reactions4.5Oxidation-Reduction (Redox) Reactions4.7Reversible Reactions: An Introduction to Chemical Equilibrium4-3Dr. Wolfs CHM 101Water As a SolventWater will dissolve ionic compounds. The charged ions become separated from each other and become surrounded by water molecules. One demonstration of this is the conduction of electricity through an ionic solution.4-4Dr. Wolfs CHM 101The electrical conductivity of ionic solutions4-5Dr. Wolfs CHM 101Sample Problem 4.1Determining Moles of Ions in Aqueous Ionic SolutionsPROBLEM:How many moles of each ion are in the following solutions?(a)5.0 mol of ammonium sulfate dissolved in water(b)78.5g of cesium bromide dissolved in water(c)7.42x1022formula units of copper(II) nitrate dissolved in water(d)35mL of 0.84M zinc chloridePLAN:SOLUTION:We have to relate the information given and the number of moles of ions present when the substance dissolves in water.(a)(NH4)2SO4(s) 2NH4+(aq) + SO42-(aq) 5.0mol (NH4)2SO42mol NH4+1mol (NH4)2SO4= 10.mol NH4+5.0mol SO42-4-6Dr. Wolfs CHM 101Sample Problem 4.1Determining Moles of Ions in Aqueous Ionic Solutionscontinuedmol CsBr 212.8g CsBr = 0.369mol CsBr = 0.369mol Cs+= 0.369mol Br1-(b)CsBr(s) Cs+(aq) + Br-(aq) 7.42x1022formula units Cu(NO3)2mol Cu(NO3)26.022x1023 formula units= 0.123mol Cu(NO3)2= 0.123mol Cu2+= 0.246mol NO31-(c)Cu(NO3)2(s) Cu2+(aq) + 2NO3-(aq) 35mL ZnCl21L 103mL = 2.9x110-2mol ZnCl2(d)ZnCl2(aq) Zn2+(aq) + 2Cl-(aq) 0.84mol ZnCl2L= 2.9x110-2mol Zn2+= 5.8x110-2mol Cl-78.5g CsBr4-7Dr. Wolfs CHM 101Water is a Polar SolventThe electron distribution in a water molecule is such that an excess of electron density is on the oxygen atom and an electron deficiency is on the hydrogen atoms. The polarity of water is what allows it to separate charged particles in ionic solutions. Its also what allows covalent compounds that are polar to dissolve in water, e.g. sugar. Although these polar compounds dissolve in water they are non-electrolytes. They do not conduct electricity since they are not charged.Water will also dissolve compounds with a polar bond to a H atom. These compounds, called acids, dissociate to give protons, H+, and anions.4-8Dr. Wolfs CHM 101The Polarity of WaterElectron distribution in molecules of H2and H2O4-9Dr. Wolfs CHM 101The dissolution of an ionic compound4-10Dr. Wolfs CHM 101Acids in water dissociate to give H+. The H+bonds with a water molecule and becomes a hydrated proton, H3O+, a hydronium ion.4-11Dr. Wolfs CHM 101Sample Problem 4.2Determining the Molarity of H+Ions in Aqueous Solutions of AcidsPROBLEM:Nitric acid is a major chemical in the fertilizer and explosives industries. In aqueous solution, each molecule dissociates and the...
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chapt04_lec - 4-1Dr. Wolfs CHM 101Chapter 4The Major...

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