Journal of Colligative Properties

Journal of Colligative Properties Colligative Properties The Effect Kind of Solution to the Boiling Point Alis Rahmawati / 113194213 Alis Rahmawati1, Anisah2, Syifa Salima3 International Chemistry Education 2011, FMIPA, Unesa abstract The research described in this paper is to know the effect kind of solution to the boiling point base from the basic theory that have learn before, The research was carried out with experimental method at Wednesday, 4thApril 2012 in Basic Chemistry Laboratory of Unesa. In this Experiment, we prepared water in the some beaker glass and then we boiled the water and measured the boiling point temperature of the water, after that we added some sugar and salt with the different mass to the beaker glass and measured the boiling point temperature of the solution. The result indicated that the boiling point of the water and the boiling point of the solution was quite different with the theory that have been learn. Finally we can conclud that the different result because of many factor that effected the boiling point like pressure, temperature, kind of solute and solvent, etc KEY WORDS : coligative properties, sugar solution, salt solution, boiling point temperature

Introduction

Background of the study Colligative Properties is one from many important subject in chemistry learning, so all of student must understand well about this material. To can understand the material, student must know the factors that include in this subject and they have to prove the theory to understand well. To do that we can through experiment method. But in this experiment, we just focus to the boiling point. Statement of the Problem The study intents to obtain answer to the following questions: 1. Prove or not that added of the sugar and salt can increase the boiling point? 2. What kind of matter that effect the boiling point of the solution? Coligative properties (or collective properties) are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles. The properties are bond together by a common origin – they all depend on the number of the number solute particles present, regradless of whether they are

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Journal of Colligative Properties atoms, ions, or molecules. The colligative properties are vapor-pressure lowering, boilingpoint elevation, freezing-point depression, and osmotic pressure. Boiling-Point The boiling point of a solution is the temperature at which its vapor pressure equals the external atmospheric pressure. Because the presence of a nonvolatile solute lowers the pressure of a solution, it must also affect the boiling point of the solution. Figure 1 shows the phase diagram of the water and the changes that occur in an aqueous solution. Because at any temperature the vapor pressure of the solution is lower than that of the pure solvent regadless of temperature, the liquid-vapor curve for the solution lies below that for the pure solvent. Consequently, the dhased solution curve untersects the horizontal line that mark P = 1 atm at higher temperature that the normal boiling point of the pure solvent. Figure1. phase diagram ilustrating the boiling point elevation and the freezing point depression of agueous solution. The dashed curves pertain to the solution, and to the solid curves to the pure solvent. As you can see, the boiling point of the solution is higher than that the of water, and the freezing point of the solution is lower than that of water.

∆Tb = Tb – T0b Since Tb>T0b, ∆Tb is the posotive quantity Boiling point elevation of nonelectrolyte solution ∆Tb ∞ m ∆Tb = Kb m Where m is the molality of the solution and Kb is the molal boiling-point elevation constant. The unit of Kb are 0C/m. It is important to understand the choise of concentration unit here.

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Journal of Colligative Properties We are dealing with a system (the solution) whose temperature is not conctant, we so can not express the concebtration units in molarity because molarity changes with temperature.

Table 1 lists values of Kb for several common solvents. Using the boiling point elevation constant and equation, we can see taht the molality m of an aqueous solution is 1.00, the boiling point will be 100.520C Boiling Point of Electrolyte solutions The colligative properties of electrolyte require a slightly different approach than the one used for the colligative properties of nonelectolytes. The reason is that electrolytes dissociate into ions in solution, and so one unit of an electrolyte compound separates into two or more particles when it dissolve. For example, each unit of NaCl dissociates into two ions Na+ and Cl-. Thus the colligative properties of a 0.1 m of solution NaCl should be twice as great as those of a 0.1 m solution containing a nonelectrolyte, sucs as sucrose To accound for this effect we must modify the equations for colligative properties as follows ∆Tb = iKbm The varieble i is the Van’t Hoff factor, which is defined as i = actual number of particles in soln after dissociation number of formula units initially dissolved in soln thus i should be 1 for all nonelectrolyte.

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Journal of Colligative Properties Method Research design Tools and materials: 1) Beaker glass 100 mL 2) Tripod and kasa 3) Thermometer 4) Spirit 5) Aquades 6) Salt (NaCl) 7) Sugar (C12H22O11) Variabel Control: mass of water 25 mL, zise of beaker glass, termometer, fire Variabel Manipulation : the mass of material that added to the water and the kind of the matter Variabel Respond : The boiling point temperature Procedure : The experiment boiled water in some beaker glass and then we added sugar and salt with the different mass to the beaker glass. Beaker glass 1A we added 25 mL water and 3,42 grams of sugar. 1B added by 25 mL water and 6,84 grams of sugar. 1C added by 25 mL water and 10,26 grams of sugar. 1D added by 25 mL water and 13,68 grams sugar. And beaker glass 2A added by 25 mL water and 0.58 gram of salt. 2B added by 25 mL water and 1,17 grams of salt. 2C added by 25 mL water and 1,75 grams of salt. 2D added by 25 mL water and 2,35 grams of salt. Finally,measured again the boiling point temperature of each solution.

Result Based from our experiment we got result of the boiling point temperature were: Non electrolyte solution 1A 25 mL water and 3,42 grams of sugar was 970C 1B 25 mL water and 6,84 grams of sugar was 970C 1C 25 mL water and 10,26 grams of sugar was 970C – 980C 1D 25 mL water and 13,68 grams sugar was 970C – 980C Alis Rahmawati

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Journal of Colligative Properties Electrolyte solution 2A 25 mL water and 0.58 gram of salt was 960C 2B 25 mL water and 1,17 grams of salt was 970C 2C 25 mL water and 1,75 grams of salt was 980C 2D 25 mL water and 2,35 grams of salt was 970C Theory calculation Known :

volume Aqueous = 25 ml Kb Aqueous = 0.520C/m T0b = 1000C

massC12H22O11 1 = 3.42 grams

mass NaCl 1 = 0.58 grams







i NaCl = 2 calculation 1. Boiling point of C12H22O11 3.42 grams m

mass 1000 . Mr massH2O

2. Boiling point of C12H22O116.84 grams m

mass 1000 . Mr massH 2 O

3.42 1000 .  0.4m 342 25 Tb  K b m  0.520 C / m  0.4m  0.208

m

Tb  Tb0  Tb


m

Tb  100 C  0.208 C  100.208 C 0

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0

0

6.84 1000 .  0.8m 342 25 Tb  K b m  0.52 0 C / m  0.8m  0.416 0 C Tb  100 0 C  0.416 0 C  100.416 0 C

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Journal of Colligative Properties 3. Boiling point of C12H22O1110.26 grams m

2. Boiling point of NaCl1.17 grams


m

10.26 1000 .  1.2m 342 25 Tb  K b m  0.52 0 C / m  1.2m  0.624 0 C m

Tb  T  Tb 0 b

0

0



4. Boiling point of C12H22O1113.68 grams m

1.17 1000 .  0.8m 58.5 25 Tb  K b m  0.52 0 C / m  0.8m  0.832 0 C m

Tb  100 0 C  0.832 0 C  100.832 0 C

Tb  100 C  0.624 C  100.624 C 0



m


1.75 1000 .  1.2m 58.5 25 Tb  K b m  0.52 0 C / m  1.2m  1.248 0 C

m

10.26 1000 .  1.6m 342 25 Tb  K b m  0.52 0 C / m  1.6m  0.832 0 C

m



Tb  100 0 C  0.832 0 C  100.832 0 C

Tb  100 0 C  1.248 0 C  101.248 0 C



m

mass 1000 m . Mr massH 2 O

mass 1000 . Mr massH2O

2.35 1000 .  1.61m 58.5 25 Tb  K b m  0.520 C / m  1.61m  1.67 0 C m

0.58 1000 m .  0.42m 58.5 25 Tb  K b m  0.52 0 C / m  0.42m  0.42 0 C


Tb  T  Tb 0 b

Tb  1000 C  1.610 C  101.67 0 C

Tb  100 0 C  0.42 0 C  100.42 0 C

Compare with the result from the theory, Table 1 : the different result between theory and experiment base from the theory Tb0 (0C) Tb (0C) 25mL H2O 100 100.208

base from the experiment Tb0 (0C) Tb (0C) 25mL H2O 94 96

No

nonelectrolyte(C12H22O11)

1A

3,42

1B

6,84

100

100,416

94

96

1C

10,26

100

100,624

96

97

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grams

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Journal of Colligative Properties 1D

13,68 electrolyte(NaCl) grams

100

100,834

base from the theory Tb0 (0C) Tb (0C) 25mL H2O 100 100,42

96

97

base from the experiment Tb0 (0C) Tb (0C) 25mL H2O 95 96

2A

0,58

2B

1,17

100

100,832

95

97

2C

1,75

100

101,248

97

98

2D

2,35

100

101,67

96

97

From the theory we got result that boiling point of pure water is 1000C and the boiling point of the sugar and salt solution increase continuously depend with the mass (number of solute particles). Between non electrolyte and electrolyte solution have different result although both of them have same numbers of particles. Moreover the result between theory and the experiment are quite different, all of the boiling point of pure water and the boiling point of solution in the experiment result were below of the theory result. Result of the boiling point solution itself unconstant although it is electrolyte solution or non electrolyte solution, they did’t have differences.

Discussion Boiling Point Elevation Base from the table 1, we know that the experiment result was quite different with the result from theory calculation. And between electrolyte and non electrolyte solution itself don’t have different, it can to be like this because: In this experiment had a lot of mistake: 1. We can’t control the variable control exactly like the fire strange from the burner so the result from the same amount of particles don’t have same result. 2. When measured the temperature we must opened the cup, so the water and the solution lose their Calor. Alis Rahmawati

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Journal of Colligative Properties 3. We did’t open the cup at same time so the temperature of the surrounding not same and it gives contribution in boiling point. Because A liquid boils at the temperature at which its vapor pressure equals atmospheric pressure. So the temperature of the surrounding doesn’t constant Although, many factor that can effected the boiling point 1. Pressure, different place have different pressure so the boiling point of the water and the solution will depend with the pressure of the surrounding 2. Room temperature, different room temperature will make different pressure 3. Kind of the solute, have different number particle 4. Kind of the solvent, have different number particle The solution can't boil at the same temperature as the pure solvent. If the vapor pressure of the solvent escaping from the solution is smaller than the vapor pressure of the pure solvent at any given temperature, the solution must be heated to a higher temperature before it boils. The lowering of the vapor pressure of the solvent that occurs when it is used to form a solution therefore increases the boiling point of the liquid. The change in vapor pressure that occurs when a solute dissolves in a solvent leads to changes in the melting point and the boiling point of the solvent as well. Because the change in vapor pressure is a colligative property, which depends only on the relative number of solute and solvent particles, the changes in the boiling point and the melting point of the solvent are also colligative properties.

Conclution

According to the theory of colligative properties, the boiling point of water is 1000C. but the result of our experiment did not show the same value because we did the experiment in low surface area that have high pressure (more than 1 atm) so the boiling point is less than the normal boiling point of water (boiling point at 1 atm). And for other solution the boiling point will decrease too. And the boiling point of electrolyte solution is higher than the non electrolyte solution. Because the electrolyte solutions have more particles than the non electrolyte solution, The Alis Rahmawati

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Journal of Colligative Properties reason is that electrolytes dissociate into ions in solution, so one unit of an electrolyte compound separates into two or more particles when it dissolve. And according to our experiment, the boiling point of NaCl (salt) solution is higher than C 12H22O11 (sugar) solution. It means that the boiling point of electrolyte solution is higher than non electrolyte solution certainly.

Refferences

Tim kimiadasar. 2012. PenuntunPraktikum Kimia DasarLanjut. Surabaya: Unesa Press Chapin, William H. 1949. Second Year College Chemistry 5th edition. New York : John Wiley & Sons, Inc Chang, Raymond. 2004. Kimia Dasarkonsep-konsepintiedisiketiga.Jakarta :Erlangg Sugiarto, Bambang.dkk. 2011. Basic Chemistry II handout.

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Journal of Colligative Properties

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