Solutions - General Chemistry - Lecture Slides, Slides of Chemistry

Download Solutions - General Chemistry - Lecture Slides and more Slides Chemistry in PDF only on Docsity! Solutions docsity.com Solutions • Solutions are homogeneous mixtures • Solute is the dissolved substance – Seems to “disappear” or “Takes on the state” of the solvent • Solvent is the substance the solute dissolves in – Does not appear to change state – When both solute and solvent have the same state, the solvent is the component present in the highest percentage • Solutions in which the solvent is water are called aqueous solutions – Water is often called the universal solvent • Solutions that contain metal solutes and solvent are called alloys docsity.com Figure 14.2: Polar water molecules interact with the positive and negative ions of a salt docsity.com The Solution Process Covalent Molecules • Covalent molecules that are small and have “polar” groups tend to be soluble in water • The ability to H-bond with water enhances solubility H C O docsity.com Figure 14.3: Polar O—H bond similar to those in the water molecule docsity.com Figure 14.4: The structure of common table sugar (called sucrose) docsity.com Figure 14.5: A molecule typical of those found in petroleum docsity.com Figure 14.6: An oil layer floating on water Oil layer Water tJ ( docsity.com Figure 14.7: Preparation of a standard aqueous solution Volume marker (calibration mark) Weighed amount of solute Wash bottle docsity.com Solution Concentration Percentage • Parts Per Hundred • % = grams of solute per 100 g of solution – Mass Percent or Percent by Mass – 5.0% NaCl has 5.0 g of NaCl in every 100 g of solution • Mass of Solution = Mass of Solute + Mass of Solvent • Divide the mass of solute by the mass of solution and multiply by 100% docsity.com Solution Concentration Molarity • moles of solute per 1 liter of solution • used because it describes how many molecules of solute in each liter of solution • If a sugar solution concentration is 2.0 M , 1 liter of solution contains 2.0 moles of sugar, 2 liters = 4.0 moles sugar, 0.5 liters = 1.0 mole sugar, etc. molarity = moles of soluteliters of solution docsity.com Figure 14.8: Acetic acid dilution tJ ( docsity.com Solution Stoichiometry • Many reactions occur in solution, therefore you need to be able to predict amounts of reactants and products in terms of concentrations and volumes as well as masses • Basic strategy is the same 1. Balance the Equation 2. Change Given Amounts to Moles 3. Determine Limiting Reactant 4. Calculate Moles of Required Substance 5. Convert Moles of the Required Substance into the Desired Unit docsity.com Example 1. Write and Balance the Reaction The reaction is a Precipitation Reaction. The reaction involves Cl-1 ions from NaCl reacting with Ag+1 ions from AgNO3 to form AgCl(s). Therefore we get Ag+1(aq) + Cl-1(aq) AgCl(s) After Balancing we get Ag+1(aq) + Cl-1(aq) AgCl(s) Calculate the Mass of Solid NaCl required to Precipitate all the Ag+1 ions from 1.50 L of a 0.100 M AgNO3 Solution docsity.com 5. Convert Moles of the Required Substance into the Desired Unit We need 0.150 moles of Cl-1 Since 1 NaCl dissociates into 1 Cl-1 The moles of NaCl needed = 0.150 moles 1 mol NaCl = 58.44 g NaCl NaCl g 8.76 NaClmol1 NaClg58.44x NaCl mol 0.150  Example Calculate the Mass of Solid NaCl required to Precipitate all the Ag+1 ions from 1.50 L of a 0.100 M AgNO3 Solution docsity.com Neutralization Reactions • Acid-Base reactions are also called Neutralization Reactions • Often we use neutralization reactions to determine the concentration of an unknown acid or base • The procedure is called a titration. With this procedure we can add just enough acid solution to neutralize a known volume of a base solution – Or visa versa docsity.com Normality • Normality is a concentration unit used mainly for acids and bases • One equivalent of an acid is the amount of acid that can furnish 1 mol of H+1 • One equivalent of a base is the amount of base that can furnish 1 mol of OH-1 • The equivalent weight is the mass of 1 equivalent of an acid or base docsity.com Normality Normality = equivalents of soluteliters of solution Liters x Normality = Equivalents of Solute docsity.com Normality and Neutralization • One Equivalent of Acid exactly neutralizes One Equivalent of Base • Can be used to simplify neutralization stoichiometry problems to the equation Nacid x Vacid = Nbase x Vbase • The volumes can be most any unit, as long as they are consistent docsity.com Example  Determine the quantities and units in the problem Acid Solution Base Solution Normality 0.45 N 0.075 N Volume 0.135 L ? L  Solve the Formula for the Unknown Quantity What volume of 0.075 N KOH is required to Neutralize 0.135 L of 0.45 N H3PO4 base acidx acid base basebaseacidacid N VNV Vx NVx N   docsity.com