Colligative Properties

Name JOANNA CELESTE M. QUINTANA run across per doed NOV. 12, 2012 Section C-1L Date submitted NOV. 21, 2012 Group enactment 3 Exercise No. 2 COLLIGATIVE PROPERTIES (Full Report) I. INTRODUCTION Colligative properties In crystalline final results, particles atomic good turn 18 close unitedly and the solute molecules or ions break up intermolecular forces among the re reply molecules, causation changes in those properties of the upshot that depend in intermolecular attraction. For display case, the halt pourboire of a closure is jell down than that of the of the utter(a) resolve and the change state stay is higher.Colligative properties of termination atomic number 18 those that depend on the concentration of solute particles in the stem, regardless of what kinds of particles ar present the great the concentration of any solute, the lower the frost fountainhead and the higher the turn point of a outcome. FREEZING POINT grueling A gas begins to freeze wh en temperature is get down to the substances frost point and the first few molecules cluster together into a crystal lattice to form a tiny quantity of unshakable.As longsighted as both solid and liquifiable phases argon present at the frost point, the roam of crystallization equals the put of run and in that location is a kinetic sense of equilibrium. When a solution freezes, a few molecules of solvent cluster together to form sublimate solid solvent and a dynamic equilibrium is lot up among the solution and the solid solvent. In the possibility of a solution, the molecules in the placid in contact with the solid solvent ar non all solvent molecule.The rate at which molecules move from solution to solid is therefore smaller that in the clear naiant state to achieve dynamic equilibrium there must be a corresponding smaller rate of avoidance of molecules from solid crystal lattice. This slower rate occurs at a lower temperature and so the freezing point of the so lution is lower than that of pellucid solvent. The change in freezing point ? Tf is proportional to the concentration of the solute in the same way as the boiling point elevation. ?Tf = Kf ? msolute ? ?soluteHere also, the proportionality unvaried Kf depends on the solvent and not the kind of solute and isolute represents the number of particles per formula unti of solute. For weewee, the freezing point constant is -1. 86 oC-kg/mole. freezing point or melting point is the temperature of transition between solid and luculent. Melting point asshole be measured more accurately than freezing points. This is becauses so in freezing point measurements, supercooling may occur which would fruit a lower than sslkdjs freezing (melting point).CHANGES IN VAPOUR PRESSURE RAOULTS virtue At the heighten of an aqueous solution, there are molecules of piddle as intimately as ions or molecules from the solute. Water molecules commode leave the facile and enter the tout phase, exerting a vaporization squelch. However, there are not as many pee molecules at the surface as in elegant irrigate, because some of them have been dis move by dissolved ions or molecules/ therefore, not as many water molecules are open to leave the swimming surface, and the vaporisation shove is lower than that of pure water at a given temperature.From this analysis, it should make senses that the vaporization wardrobe of the solovent above the solution, Psolvent, solution, that is , to their mole member. Thus, since Psolvent ? Xsolvent, we stinker write Psolvent = Xsolvent ? K (where K is a constant). This equivalence tells you that, if there are unaccompanied half as many solvent molecules present at the surface of a solution as at the surface of the pure liquefied, thus the vapour pressure of the solvent above the solution entrust only be half as great as that of the pure solvent at the same temperature. If we are relations only with pure solvent, the above equation be comes Posolvent = Xsolvent ?K where Posolvent is the vapour pressure of the pure solvent and Xsolvent is equal to 1. This means that Posolvent = K that is, the constant K is just the vapour pressure of the pure sovent. Substituting for K in the foremost equation, we arrive at an equation called Raoults right Psolvent = Xsolvent ? Posolvent If the solution contains more than one volatile component, hence Raoults fairness can be written for any one such component, A, as PA = XA ? PoA kindred this ideal gas honor, Raoults law is a description of a alter model of a solution.An ideal solution is one that obey Raoults law/ although most solution are not ideal, just as most gases are not ideal, we use Raoults law as good approximation to solution behaviour. In any solution, the mole fraction of the solvent will always be less than 1, so the vapour pressure of the solvent everyplace an ideal solution (Psolvent) must be less than the vapour pressure of the pure solvent (Posolvent). T his vapour pressure lowering, ? Psolvent, is given by ? Psolvent = Psolvent ? Posolventwhere Psolvent Posolvent change state point elevationRaoults law tells us that the vapour pressure of the solvent over a solution must be lower than that of the pure solvent. Assume for example that you have a solution of a non-volatile solute in the volatile solvent benzine ? ? ? ? II. MATERIALS A. Reagents 4. 00 g naphthalene 0. 20 g unheard-of solute A unknown solute B (assigned meter per group) distilled water B. Apparatus 250-mL beaker 400-mL beaker 100-mL graduated cylinder strain tubes thermometer press stand, iron ring, iron clamp hot plate C. other Apparatus wire gauze waver paper graphing paper timer III. social function Freezing argue of NaphthaleneIn a refined and dry test tube, 2. 0 g of naphthalene was weighed. To measure the temperature while heating, a thermometer was hang by meander paper at the lip of the test tube. It was placed in a water bath with the water lev el above the sample in the test tube. To avoid the contact of the test tube to the sink in of the bath, it was supported by an iron clamp. The water bath was then change until the entire sample has smooth and until the temperature of the sample reached 90o C. The flame was put mangle and the temperature reading was save every 15 seconds until the temperature has fallen to 70oC.The set up was put aside for the next part of the experiment. selective information gathered were tabulated and plotted for analysis and evaluation. Freezing Point Depression of Naphthalene Pre weighed 0. 20 g of unknown solute A was added to the previous set up of naphthalene. The same procedure was do with it. The thermometer was again suspended at the mouth of the test tube by tissue paper. With the help of iron clamp, it was again placed in a water bath, with the water level above the sample in the test tube, to avoid contact to the bottom of the bath.The water bath was then heated until the entire s ample of unknown solute A and naphthalene has melted. When the temperature reached 90oC, the flame was put off. The temperature reading was recorded every 15 seconds until the temperature has fallen to 70oC. information was also tabulated and plotted together with the entropy from freezing point of naphthalene. Boiling Point of Water In a 250-mL beaker, 100-mL of distilled water was boiled until it completely boiled. The temperature reading was recorded. In a separate 250-mL beaker, 0. 20 g of unknown solute B was dissolved in 100-mL distilled water.This was also heated until it finally boiled. The boiling point was also recorded. It was tabulated together with the boiling points of solutions with change amounts of solute from other groups. Comparison was do for evaluation of the results. IV. DATA/OBSERVATIONS Table 1. 1. Observations on cooling of naphthalene at 15-second intervals. Time (sec. )Temperature (oC)Appearance 1590clear liquid 3090clear liquid 4587clear liquid 6086cl ear liquid 7585clear liquid 9085clear liquid 10584clear liquid 12084clear liquid 13583clear liquid 15083clear liquid 16582clear liquid 18081clear liquid 9581clear liquid 21080clear liquid 22580clear liquid 24079clear liquid 25579clear liquid 27078clear liquid 28577clear liquid 30077clear liquid 31576solidification 33075solidification 34575 36075 37575 39075 40575 42075 43575 45075 46575 48075 49575 51075 52575 54075 55575 57075 58575 60075 61575 63075 64574 66074 67574 69074 70574 72073 73573 75073 76572 78072 79571 81070 freshet of naphthalene utilise (g) 2. 00 g Table 1. 2. Observations on cooling of solution of naphthalene and unknown solute at 15-second interval. Time (sec. )Temperature (oC)Appearance 1590clear liquid 3090clear liquid 587clear liquid 6086clear liquid 7585clear liquid 9085clear liquid 10584clear liquid 12084clear liquid 13583clear liquid 15083clear liquid 16582clear liquid 18081clear liquid 19581clear liquid 21080clear liquid 22580clear liquid 24079clear liquid 25579clear liquid 27078clear liquid 28577clear liquid 30077clear liquid 31576clear liquid 33075 34575 36075 37575 39075 40575 42075 43575 45075 46575 48075 49575 51075 52575 Mass of naphthalene utilize (g) 2. 00 g mass of unknown solute B (g) 0. 20 g Table 1. 3. selective information on freezing point embossment of naphthalene. Mass of naphthalene use (g)2. 0 g Mass of unknown solute A used (g)0. 20 g Mass of solution (g)2. 20 g Freezing point of pure naphthalene (oC)75 oC Freezing point of solution (oC)73 oC Freezing point difference of pure naphthalene and of solution (oC) Molality of solution (mol/kg) Moles of solute used (mole) Molecular mass of solute (g/mole) Table 1. 4. abstract of data on boiling points of solutions with varying amounts of solute. Group No. Amount of solute B used (g)Boiling point (oC) 100 10. 5099. 0 21. 0090. 0 31. 5099. 5 42. 0099. 5 52. 50100 V. countersign ? ? ? ? VI. CONCLUSION ? VII. LITERATURE CITED/BIBLIOGRAPHY