General Chemistry 1
General Chemistry 1 CHEM 121
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Chapter 11 States of Matter Liquids and Solids CHEM 121 Dr Miller 111 Comparison of Gases Liquids and Solids Gases are compressible fluids Liquids are relatively incompressible fluids Solids are nearly incompressible and rigid Liquid 112 Phase Transitions A change of state or phase transition is a change of a substance from one state liquid solid gas to another The specific name or names for each of these transitions are given below Sublimation e 0 Melting tnston Vaporizntion V o gt gt 9 0 q Freezing Condensation a liquefaction a a Solid Liquid Gas Deposition The vapor pressure of a liquid at a particular temperature is the partial pressure of the vapor over the liquid measured at equilibrium When a liquid is placed in a closed vessel the partial pressure of its vapor increases over time until it reaches the equilibrium At equilibrium evaporation and condensation continue to occur but do so at the same rate This situation is called a dynamic equilibrium X0 Xg equilibrium Equilibrium vaporization attained Rates become equal Rate Rate of condensation Time gt The vapor pressure depends on the liquid and on the temperature Volatie evaporates readily high vapor pressure V upor pressure mmHg 800 760 700 100 500 400 300 200 l 0 chloroform Dicthyl other Tcmpcruturc C 60 Water C arbon tetrachloride 80 100 The boiling point is Aunospheric the temperature at pressure which the vapor pressure is equal to l 4 the pressure on the i Vapor The normal boiling k bubble point is measured at 1 atmosphere pressure atmospheric pressure At this temperature bubbles of gas form within the liquid liquid usually I 397 l When the pressure on the liquid increases as is the case with a pressure cooker the boiling point increases Conversely when the pressure on the liquid decreases as is the case at high altitude the boiling point decreases httpwwwvoutubecomwatchv9q5qEZ Gankampfeaturerelated The freezing point is the temperature at which a pure liquid changes to a crystalline solid for freezes The melting point is the temperature at which a crystalline solid changes to a liquid for melts Any change of state requires that energy be added to or removed from the system For water there are two regions that remain at the same temperature even as heat is added Those represent regions of phase change Steam 120 100 Water and steam Water Ice and water Temperature 0C 0 C Time gt Heat added at constant rate The heat of fusion AHfUS is the heat needed to melt a solid It is given in kJmol For water the phase change is represented by HZOs 9 HZOI Ahqu 601 kJmol The heat of vaporization AHvap is the heat needed to vaporize a liquid It is given in kJmol For water the phase change is represented by HZOI 9 HZOg Ahvap 407 KJmol Consider a time t 1 when enough time has passed for the l l I system to reach equilibrium i 1How will the level of the liquid H2O l l compare to that at 1 0 l 2 How will the vapor pressure in the r flask compare to that at 1 0 higher 3 How will the number of H20 molecules in the vapor state compare to that at 1 0 higher 4 How does the rate of evaporation in this system compare to the rate of condensation t1 higher Consider a time t 2 when some time has passed but the 1 l I system has not reached l m l equilibriu 1How will the level of the liquid H20 compare to that at 11 lower i f 0 0 i quot 2 How will the vapor pressure in the flask compare to that at 1 2 higher 3 How will the number of H20 l molecules in the vapor state g 0 compare to that at 1 1 higher 4 How does the rate of evaporation in this system compare to the rate of condensation Equal at P llilihl lnP Diethyl ether Chloroform Water Carbon tetrachloride 260 280 300 320 340 360 380 400 lT X 103 The Clausius Clapeyron equation describes this relationship LnP2P1 mapRum 1T2 R 8314510 Jmol K n AH must be given in vap Jmol This equation can be used to find the vapor pressure the heat of vaporization or the annro II Ira The fuel requirements of some homes are supplied by propane gas C H8 which is contained as a liquid in steel cylinders If a home uses 240 kg of propane in an average day how much heat must be absorbed by the propane cylinder each day to evaporate the liquid propane forming the gas that is subsequently burned The heat of vaporization of propane is 169 kJmol The vapor pressure of diethyl ether commonly known as simply ether is 4398 mmHg at 200 C The heat of vaporization of ether is 292 git161What is the vapor pressure of ether at 113 Phase Diagrams A phase diagram is a graphical way to summarize the conditions pressure volume under which the various states of a substance are stable Phases are separated by lines that represent equilibrium between those phases The triple point is the point where all three phases are in equilibrium Pressure atm Phase Diagram for H20 Why does the solidliquid phase line slant to the left Normal Freezing point of water 0 0 C 100 C 39 Boiling point 100 Temperature Boiling point 78 Pressure atm Temperature gt Why does CO2 sublime at STP The critical point gives the temperature critical temperature TC at which the liquid state can no longer exist and the pressure at that temperature critical pressure Above this temperature and pressure there is only one state a superficial fluid uglieed to 39pay particular attention to changes in water If you like eggs that are boiled wouldvyou have to cook them for a longer or a gg you like Be sure to explain your answer onger 114 Properties of Liquids Surface Tension and Viscosity Surface tension is the energy required to increase V the surface area ofa liquid y Surface or by a unit amount The values are given in 17m2 It arises because the molecules at the surface of a liquid experience a net force toward the center of the liquid cohesive forces Surface tension is also related to capillary rise In this phenomenon when a very smalldiameter glass tube a capillary is placed in water the water rises The water is attracted to the glass adhesive force so a thin film moves up the surface of the glass This action expands the surface area so the water column rises to counteract it The process then repeats itself Capillary Water vs 3 Meniscus Water Capillary Meniscus Mercury Viscosity is the resistance to flow exhibited by liquids and gases For example syrup vs water Syrup is more viscous than water IQ TABLE 112 I Properties of Some Liquids at 20 C Molecular Weight Vapor Pressure Surface Tension Viscosity Substance amu mmHg Jmz kgms Water H30 18 18 x 10 73 x 10 2 10 x 10 3 Carbon dioxide CO2 44 43 x 104 12 x 10 3 71 x 10 5 PentaneC5H12 72 44 x 102 16 x 1072 24 x 10 4 Glycerol 11803 92 16 x 10 4 63 x 10 2 15 x 100 Chloroform CHCI3 119 17 x 102 27 x 10 2 58 x 10 4 CaIbon tetrachloride CCL 154 87 X 10l 27 X 10 2 97 X 10 4 Bromoform 011313 253 39 x 10quot 42 x 10 2 20 gtlt 10 3 115 Intermolecular Forces Explaining Liquid Properties Neon liquefies at 246C at 1 atm AHvap for liquid neon is 177 kJmol The AHvap for neon is due to Energy needed to push back the atmosphere when the vapor forms 023 kJmol Energy needed to overcome intermolecular attractions 154 kJmol Intermolecular Forces Three types of Intermolecular forces Types of Intermolecular and Chemical Bonding Interactions molecules or atoms I Approximate d I I Type of Interactlon Energy kJmol Intermolecular London forces and Van der dipole dipole London 0 to 10 hydrogen bondan 10 to 40 Chemical bonding f0 39 Ionic 100 to 1000 Covalent 100 to 1000 The term van der Waals forces is a general term that includes both dipole dipole forces and London forces Polar molecules exhibit dipoledipole forces that result in alignment of the molecules ma ang Hao i ad dao o a9 9 9 Solid Liquid A B London Dispersion Forces In nonpolar molecules there is no dipoledipole force yet there is still a force of attraction In 1930 Fritz London explained this relationship with what we now call the London forces In a nonpolar molecule the charge is uniformly distributed over time But in any one instant39the charge is not uniformly distributed In that 243 instant there is an instantaneous dipole London forces are the weak attractive forces between molecules resulting from the small instantaneous dipoles that occur because of the varying positions of the electrons during their motion about the nuclei All molecules exhibit London forces London forces increase with increasing mass atomic number because the presence of more electrons causes a stronger instantaneous dipole London forces are also larger for more polarizable more easily distorted molecules fffi T515171 PllH C HPII H f C f C H H f f f H H H H H I H H H H Cl H H H C H H Name penlune 2melhylhul une lZIimelhylpropune Boiling Point 36 C L 95 AHW 258 kJmol 247 kJmol 228 kJmol All 3 molecules have the same formula same MM Boiling points AHvap vary widely due to different London forces The straightchain compound has the strongest intermolecular forces and the highest heat of vaporization because it is most flexible and therefore most polarizable The most compact compound has the weakest intermolecular forces and the lowest heat of vaporization How do intermolecular forces affect Vapor pressure The stronger the intermolecular forces the lower the vapor pressure Boiling point The stronger the intermolecular forces the higher the boiling point Surface tension The stronger the intermolecular forces the higher the surface tension Viscosity The stronger the intermolecular forcesn the more viscious the liquid TABLE 112 Properties of Some Liquids at 20 C Molecular Weight Vapor Pressure Surface Tension Viscosity Substance amu mmHg Jml kgms Water H20 18 18 x 101 73 x 10 2 10 x 10 3 Carbon dioxide CO2 44 43 x 104 12 x 10 3 71 x 10 5 Pentane 5le 72 44 X 102 16 x 10 2 24 x 10 4 Glycerol C3H803 92 16 x 10 4 63 x 10 2 15 X 100 Chloroform CHC13 119 17 x 102 27 x 10 2 58 x 10 4 Carbon tetrachloride CC14 154 87 X 1039 27 X 10 2 97 X 10 4 Bromoform CHBr3 253 39 x 100 42 x 1072 20 x 1073 i l i i H O H H CIJ Cl Cl H H Cl O H I 3 H H H H Water Glycerol Methanol Hydrogen Bonding Hydrogen bonding is a weak attractive force that exists betweei hydrogen atoms bonded to a very l quot V electronegative atom X and a lone pair of electrons on another a small electronegative atom Y bonds 39 39 Hydrogen X H Y Most often X is F O or N the i smallest most electronegative elements Boiling point 0C 100 80 60 40 20 H20 80 Boiling point 0C lOO 120 l40 HZSe 160 Has 20 40 60 80 100 120 Molecular mass A 20 40 60 80 100 Molecular mass B 120 Identify the intermolecular forces that you would expect for each of the following substances a 02 b H202 c CHBr3 116 Classification of Solids A solid is nearly incompressible welldefined shape because the units atoms molecules ions making up the solid are in close contact and reside in fixed positions or Sites TABLE 4 I Types of Solids Attractive Forces Between Type of Solid Structural Units Structural Units Examples Molecular Atoms or molecules Intennolecular forces Ne H20 C03 Metallic Atoms positive cores Metallic bonding Fe Cu Ag surrounded by extreme delocalized electron sea bond Ionic Ions Ionic bonding CsCl NaCl ZnS Covalent network Atoms Covalent bonding Diamond graphite asbestos Types of Solids A molecular solid consists of atoms or molecules It is held together by intermolecular forces A metallic solid consists of the positive cores of metal atoms It is held together by metallic bonding a sea of delocalized electrons An ionic solid is composed of cations and anions It is held together by ionic bonds the electrical attractions between oppositely charged particles A covalent network solid consists of atoms These are held together in large chains or networks by covalent bonds Graphite Diamond Properties of Solids What would have the lowest melting point A ionic solid B covalent network solid C molecular solid The melting points of ionic solids vary owing to differences in lattice energies that reflect the charge and size of the ions involved The melting points of metals vary widely Hardness depends on how easily the structural units can be moved relative to one another Molecular solids tend to be soft By contrast threedimensional covalent network solids such as diamond are very hard lonic compounds are brittle because they tend to fracture easily along crystal planes Metals are malleable so that they can be easily shaped by hammering Conductivity Metals are good electrical conductors because of their delocalized valence electrons lonic solids do not conduct electricity When melted however they do conduct electricity They also conduct electricity when they are dissolved in water TABLE 115 Properties of the Different Types of Solids Hardness and Electrical Type of Solid Melting Point Brittleness Conductivity Molecular Low Soft and brittle Nonconducting Metallic Variable Variable hardness Conducting malleable Ionic High to very Hard and brittle Nonconducting solid high conducting liquid Covalent network Ve1y high Very hard Usually nonconducting Chapter 12 Solutions CHEM 121 Dr Miller 121 Types of Solutions A solution is composed of two parts the solute and the solvent Solute The gas or solid in a solution of gases or solids or the component present in the smaller amount Solvent The liquid in the case of a solution of gases or solids or the component present in the larger amount Fluids that mix with or dissolve in each other in all proportions are said to be miscible Fluids that do not dissolve in each other are said to be immiscible 122 Solubility and the Solution Process A saturated solution is in equilibrium with respect to the amount of dissolved solute The rate at which the solute leaves the solid state equals the rate at which the solute returns to the solid state The solubility of a solute is the amount that dissolves in a given quantity of solvent at a given temperature An unsaturated solution is a solution not in equilibrium with respect to a given solute more can be added A supersaturated solution is a solution that contains more dissolved substance than a saturated solution does This occurs when a solution is prepared at a higher temperature and is then slowly cooled Solubility can be understood in terms of two factors The natural tendency toward disorder favors dissolving The relative force between and within species must be considered Stronger forces within solute species oppose dissolving Stronger forces between species favor dissolving Molecular solutions like dissolves like Solubility of ionic solids in water is determined by two factors Hydration energy ion dipole force between the ion and the solvent Lattice energy force between ions In most cases solubility increases with increasing temperature However for a number of compounds solubility decreases with increasing temperature 123 Effects of Temperature and Pressure on Solubility Henry s law describes m the effect of pressure on gas solubility The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the solution 1 Piston Gaseous C02 Aqueous solution of S kHP S gas solubility kH Henry s law constant for the gas P partial pressure of the gas over the solution Concept Check 123 Most sh have a very dif cult time suwiving at elevations much above 3500 m How could Henry s law be used to account for this fact Helium oxygen mixtures are sometimes used as the breathing gas in deepsea diving At sea level where the pressure is 10 atm the solubility of pure helium in blood is 094 gmL What is the solubility of pure helium at a depth of 1500 feet Pressure increases by 10 atm for every 33 feet of depth so at 1500 feet the pressure is 46 atm For a helium oxygen mixture the solubility of helium will depend on its initial partial pressure which will be less than 10 atm 124 Ways of Expressing Concentration The concentration of a solute can be quantitatively expressed in several ways 99 F Molarity Mass percent of solute Molality Mole fraction Molarity is the moles of solute per liter of solution It is abbreviated as M M moles of solute moles of solution Mass percentage of solute is the percentage by mass of solute in a solution mass percentage of solute grams of solute grams of solution An experiment calls for 360 g of a 500 aqueous solution of potassium bromide Describe how you would make up such a solution Molality is the moles of solute per kilogram of solvent It is abbreviated as m m moles of solute kilograms of solvent Mole fraction is the moles of component over the total moles of solution It is abbreviated X X moles of solute total moles of solution A solution of iodine l in methylene chloride CHZCI2 contains 500 g l2 and 560 g CHZCIZ What is the mole fraction of each component in this solution A bottle of bourbon is labeled 94 proof meaning that it is 47 by volume of alcohol in water What is the mole fraction of ethyl alcohol C H5OH in the bourbon The density of ethyl alcohol is 680 gmL A 36 m solution of calcium chloride CaClz is used in tractor tires to give them weight The addition of CaCl2 also prevents water in the tires from freezing at temperatures above 20 C What are the mole fractions of CaCl2 and water in such a solution Citric acid HC6H7O7 is often used in fruit beverages to add tartness An aqueous solution of citric acid is 2331 m HC6H7O What is the molarity of the solution The density of the solution is 11346 gmL An aqueous solution of ethanol is 141 MC2H5OH The density of the solution is 0853 gcm3 What is the molality of ethanol in the solution Colligative properties of solutions are properties that depend on the concentration of the solute or ions in solution but not on the chemical identity of the solute How does the presence of solute molecules affect 1 2 Boiling point higher 3 4 Osmotic pressure Vapor pressure lower Freezing point lower 125 Vapor Pressure of a Solution The vapor pressure of a solution P is less than the vapor pressure of the pure solvent solvent P P lt Psolvent When the solute is nonvolatile the vapor pressure of a solution is the mole fraction of the solvent times the vapor pressure of pure solvent P x solution P solution solvent solvent ConcA lt Como quot ConcA 2 Como PAgtP Jar gt PB PA ij 10B Vapor pressure lowering is directly proportional to the regardless of the solute When the solute is it has no appreciable itself and forms an When the solute is a results If a volatile solute is present will the vapor pressure of the solvent be a higher or b lower than the ideal Eugenol C10H1202 is the chief constituent of oil of clove This pale yellow liquid dissolves in ethanol CZH5OH it has a boiling point of 255 C As a result we know eugenol s vapor pressure is very low it can be considered nonvolatile What is the vaporpressure lowering at 200 C of a solution containing 856 g of eugenol in 500 g of ethanol The vapor pressure of ethanol at 200 C is 446 mmHg 126 BoilingPoint Elevation and FreezingPoint Depression The boiling point of a solution is than the boiling point of pure I solvent Freezing point of pure solvent Freezing point of solution Pre 5 sure The freezing point of a solution is than i AT Al the freezmg pomt of 39r f w Temperamrel C httpwwwvoutubecomwatchvue2EcmOch httpwww mvsfgcecomvideovid 1 027942 A solution is made up of eugenol CmH 20 n diethyl ether ether If the solution IS 655 m eugenol in ether what are the freezing point and the boiling point of the solution The freezing point and the boiling point of pure ether are 1163 C and 346 C respectively The freezingpoint depression and boilingpoint elevation constants are 179 Cm and 202 Cm respectively An 112g sample of sulfur was dissolved in 400 g of carbon disulfide The boilingpoint elevation of carbon disulfide was found to be 263 C What is the molar mass of the sulfur in the solution What is the formula of molecular sulfur The boiling point elevation constant Kb for carbon disulfide is 240 Cm 127 Osmosis Osmosis is the phenomenon of solvent flow through a to equalize on both sides A semipermeable membrane allows molecules to pass through but not molecules Osmotic pressure 7 is equal to the pressure that when applied Water 0 Q 0 0 e 9 m cogs a 0a 0 o a g 0 G1ucose o 0 9 0 0 r o 3937 a 0 0 9 9 0 a 397 i0 0 00 000 9quot 0 390 a 00 09 a 9090 00 90 al 000 a 900 800 0960 O a a 0 a 0 0 0 9 00 0 Semipermeable membrane Osmotic Pressure Thistle iop funnel Glucose molecule Glucose am solution molecule Water Membrane Before equilibrium is reuche After equilibrium is reached Dextran a polymer of glucose units is produced by bacteria growing in sucrose solutions Solutions of dextran in water have been used as a blood plasma substitute At 21 C what is the osmotic pressure in mmHg of a solution containing 150 g of dextran dissolved in 1000 mL of aqueous solution if the average molecular mass of the dextran is 40 x 108 amu