Solutions - Mamp;amp; M0s Chemistry Class

Slide Title,Body Text,Second Level,Third Level,Fourth Level,Fifth Level,39,Solutions,Some Definitions,A solution is a,mixture of 2 or more substances in a single phase.,One part is usually called the,SOLVENT,and the other part is the,SOLUTE,.,Parts of a Solution,SOLUTE, the part of a solution that is being dissolved (usually the lesser amount),SOLVENT, the part of a solution that dissolves the solute (usually the greater amount),Solute + Solvent = Solution,Solute,Solvent,Example,solid,solid,Zinc, Copper,solid,liquid,Salt, Water,gas,solid,Hydrogen gas, Metal,liquid,liquid,Creamer, Coffee,gas,liquid,Carbon Dioxide, water,gas,gas,Nitrogen in Oxygen,Definitions,Solutions can be classified as,saturated,or,un,saturated,.,An,unsaturated,solution contains less than the maximum amount of solute that can dissolve at a particular temperature,A,saturated,solution contains the maximum quantity of solute that dissolves at that temperature.,Definitions,SUPERSATURATED SOLUTIONS:,contains more solute than should be possible to be dissolved,Supersaturated solutions are unstable,only temporary,2 Ways to make a supersaturated solution:,Warm the solvent so that it will dissolve more, then cool the solution,Evaporate some of the solvent carefully so that the solute does not solidify and come out of solution.,Supersaturated,Sodium Acetate,One application of a supersaturated solution is the sodium acetate “heat pack.”,Two types of aqueous Solutions,Ionic compounds will disassociate in water,Covalent Compounds do not disassociate they only dissolve,Dissasociation,How do we know ions are present in aqueous solutions?,The solutions Conduct Electricity,They are called,ELECTROLYTES,HCl, MgCl,2, and NaCl are,strong electrolytes,.,They dissociate completely (or nearly so) into ions.,Aqueous Solutions,Aqueous Solutions,Some compounds dissolve in water but do not conduct electricity. They are called,nonelectrolytes.,Examples include:,sugar,ethanol,ethylene glycol,Rate of Dissolution,Factors that affect the,rate of dissolution,(make solute dissolve faster):,Increase the surface area of the solute (crush solute into small pieces),Agitate the solution (brings solvent into increased contact with solute),Heating the solvent (increases KE of solute particles on surface),Factors that affect a substances,solubility,:,Amount of solute (in grams),Amount of solvent (in grams),Specified temperature (in C),All 3 of these factors are shown on a solubility curve.,A solubility curve shows the trend in solubility of a substance at a given temperature range,Three types of solutions, in terms of solubility (see solubility curve):,On the line,Below the line,Above the line,How many grams of NaCl are required to make a saturated solution at 50C?,A supersaturated solution at 70C contains 132 g of solute in 100 g of water. Which compound does this solution contain?,Which of these is an unsaturated solution?,F- 60 g of KNO,3,dissolved in 200 g of H,2,O at 10C,G -90 g of NaNO,3,dissolved in 100 g of H,2,O at 20C,H -35 g of KCl dissolved in 100 g of H,2,O at 60C,J -40 g of NaCl dissolved in 75 g of H,2,O at 90C,4. Which compound is least soluble in 100g of water at 25C?,5. Is 45g of KCl at 80C: Saturated, unsaturated, or supersaturated?,Concentration of Solute,The amount of solute in a solution is given by its,concentration,.,Molarity,(,M,),=,moles solute,liters of solution,Find the equation on your Reference Sheet,1.0 L of water was used to make 1.0 L of solution. Notice the water left over.,PROBLEM: Dissolve 5.00 g of NiCl,2,6 H,2,O in enough water to make 250 mL of solution. Calculate the Molarity.,Step 2:,Calculate moles of the Solute,Step 3:,Calculate Volume in L,Step 1,List out all your variables,M (mol/L)= ?,moles=?,Volume(L)=?,Step 4:,Calculate Molarity using,the appropriate equation,USING MOLARITY,What mass of oxalic acid,H,2,C,2,O,4, is,required to make 250. mL of a 0.0500 M,solution?,Learning Check,How many grams of NaOH are required to prepare 400. mL of 3.0,M,NaOH solution?,1)12 g,2)48 g,3) 300 g,An,IDEAL SOLUTION,is one where the properties depend only on the concentration of solute.,Need conc. units to tell us the number of solute particles per solvent particle.,The unit “molarity” does not do this!,Concentration Units,Two Other Concentration Units,grams solute,grams solution,MOLALITY, m,% by mass,=,% by mass,m of solution,=,mol solute,kilograms solvent,Calculating Concentrations,Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H,2,O. Calculate molality and % by mass of ethylene glycol.,Calculating Concentrations,Calculate molality,Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H,2,O. Calculate m & % of ethylene glycol (by mass).,Calculate weight %,Learning Check,A solution contains 15 g Na,2,CO,3,and 235 g of H,2,O? What is the mass % of the solution?,1) 15% Na,2,CO,3,2) 6.4% Na,2,CO,3,3) 6.0% Na,2,CO,3,Using mass %,How many grams of NaCl are needed to prepare 250 g of a 10.0% (by mass) NaCl solution?,Try this molality problem,25.0 g of NaCl is dissolved in 5000. mL of water. Find the molality (m) of the resulting solution.,m = mol solute / kg solvent,25 g NaCl 1 mol NaCl,58.5 g NaCl,= 0.427 mol NaCl,Since the density of water is 1 g/mL, 5000 mL = 5000 g, which is 5 kg,0.427 mol NaCl,5 kg water,= 0.0854 m salt water,Colligative Properties,On adding a solute to a solvent, the properties of the solvent are modified.,Vapor pressure decreases,Melting point decreases,Boiling point increases,Osmosis is possible (osmotic pressure),These changes are called,COLLIGATIVE PROPERTIES,.,They depend only on the,NUMBER,of solute particles relative to solvent particles, not on the,KIND,of solute particles.,Change in Freezing Point,The freezing point of a solution is,LOWER,than that of the pure solvent,Pure water,Ethylene glycol/water,solution,Change in Freezing Point,Common Applications of Freezing Point Depression,Propylene glycol,Ethylene glycol deadly to small animals,Common Applications of Freezing Point Depression,Which would you use for the streets of Bloomington to lower the freezing point of ice and why? Would the temperature make any difference in your decision?,sand, SiO,2,Rock salt, NaCl,Ice Melt, CaCl,2,Change in Freezing Point,Change in Boiling Point,Common Applications of Boiling Point Elevation,Boiling Point Elevation and Freezing Point Depression,T = Kmi,i = vant Hoff factor = number of particles produced per molecule/formula unit. For covalent compounds, i = 1. For ionic compounds, i = the number of ions present (both + and -),CompoundTheoretical Value of i,glycol1,NaCl2,CaCl,2,3,Ca,3,(PO,4,),2,5,Boiling Point Elevation and Freezing Point Depression,T = Kmi,Substance,K,b,benzene,2.53,camphor,5.95,carbon tetrachloride,5.03,ethyl ether,2.02,water,0.52,m = molality,K = molal freezing point/boiling point constant,Substance,K,f,benzene,5.12,camphor,40.,carbon tetrachloride,30.,ethyl ether,1.79,water,1.86,Change in Boiling Point,Dissolve 62.1 g of glycol (1.00 mol) in 250. g of water. What is the boiling point of the solution?,K,b,= 0.52,o,C/molal for water (see K,b,table).,Solution,T,BP,= K,b, m i,1.Calculate solution molality = 4.00 m,2.T,BP,= K,b, m i,T,BP,= 0.52,o,C/molal (4.00 molal) (1),T,BP,= 2.08,o,C,BP = 100 + 2.08 = 102.08,o,C (water normally boils at 100),Calculate the Freezing Point of a 4.00 molal glycol/water solution.,K,f,= 1.86,o,C/molal (See K,f,table),Solution,T,FP,= K,f, m i,= (1.86,o,C/molal)(4.00 m)(1),T,FP,= 7.44,FP = 0 7.44 = -7.44,o,C(because water normally freezes at 0),Freezing Point Depression,At what temperature will a 5.4 molal solution of NaCl freeze?,Solution,T,FP,= K,f, m i,T,FP,= (1.86,o,C/molal) 5.4 m 2,T,FP,o,C,FP = 0 20.1 = -20.1,o,C,Freezing Point Depression,Preparing Solutions,Weigh out a solid solute and dissolve in a given quantity of solvent.,Dilute a concentrated solution to give one that is less concentrated.,ACID-BASE REACTIONSTitrations,H,2,C,2,O,4,(aq) + 2 NaOH(aq) -,acid,base,Na,2,C,2,O,4,(aq) + 2 H,2,O(liq),Carry out this reaction using a,TITRATION,.,Oxalic acid,H,2,C,2,O,4,Setup for titrating an acid with a base,Titration,1. Add solution from the buret.,2. Reagent (base) reacts with compound (acid) in solution in the flask.,Indicator shows when exact stoichiometric reaction has occurred. (Acid = Base),This is called NEUTRALIZATION.,