Determination of Partial Molal Volume

CHAPTER I
INTRODUCTION

1.1 Background

Thermodynamics is a science-related operational microscopic properties which basically can be measured. The purpose of this study is to predict the types of chemical and physical processes that may be, and in what conditions and quantitatively calculate equilibrium properties during a process.

There are three main partial molal thermodynamic properties, namely:
Partial molal volume of the components in solution.
Partial molal enthalpy (also referred to as the differential heat of solution).
Partial molal free energy (called the chemical potential).

Molal volume of solution is defined as the volume expansion that occurs when one mole of component i added to the partial molal.Volume can also be defined as a contribution to the volume, of one component in a sample of the total volume. Partial molal volumes of a mixture varies depending on the composition, because each type of molecule to change its environment, if the composition changed from pure A to B pure. Nature partial molal most easily illustrated by the volume of contributions to the partial molal volumes of one component in the sample to volume total.

In this experiment, we will try to determine the partial molal volume of a solution, where we will find the relation between the partial molal volume with concentration.

1.2 Experiment Objectives
1.2.1 Experimental Purposes

The purpose of this experiment was to study and understand the method of determination of partial molal volume of solution.

1.2.2 Experiment objectives

The purpose of this experiment is to determine the partial molal volume of sodium chloride solution as a function of solution concentration using piknometer.


1.3 Principle Experiment

The principle of this experiment is the determination of partial molal volume of sodium chloride with different concentrations by measuring the density of the solution using piknometer.

CHAPTER II
LITERATURE REVIEW

In thermodynamics there are two types of variables, namely:
Extensive variables that depend on the amount of phase, eg, V, U, H, S, of A, G.
Intensive variables that do not depend on the number of phases, for example: P and T (Taba and Fauziah, 2006).

Molal volume of solution (V 1) is defined as the volume expansion that occurs when 1 mole of component i added to the solution. The total volume of solution containing 1000 g (55.51 mol) of water and solutes mmol given by the equation:

V = N 1 V 1 + N 2 V 2 = 55.51 V 1 + m V 2

Suppose V 1 ˚ is the molal volume of pure water (V 1 = 18.016 ˚ / 0.997044 = 18.069 cm 3 at 25 ˚ C), the molal volume of solute ( ) Is defined as follows:

V = N 1 V 1 ˚ + N 2 V 2 = 55.51 V 1 ˚ + m or

Where d = density of solution

d 0 = density of pure solvent

M 2 = molecular weight solutes

Thus obtained:
Where We = weight of empty piknometer

Wo = Weight piknometer containing pure water

We = Weight piknometer containing solution

(Taba and Fauziah, 2006).

Partial molal properties are most easily illustrated by the volume of contributions to the partial molal volume of one component in a sample of the total volume. Stating the total volume of mixture V, using the following:

V = n a. V a = n b. V b

The reasons underlying this simple result is as follows: imagine a very large sample from a mixture of specific composition. Then if a number n a substance A added for N a. V a. sample now occupies a larger volume, but the ratio remains the same components (Atkins, 1994).

Partial molar volume of a substance can be interpreted as a change in volume when 1 mol of the substance added to a mixture of a very large volume. The total volume of the mixture can be interpreted as the partial molar volume of component

There are three main partial molal thermodynamic properties, namely: (i) partial volume of component-kompenen in solution, (ii) the partial molal enthalpy, and (iii) the partial molal free enegi (Glance, 2009).

Partial volume (and the partial molal quantity generally) can be measured in several ways. One method is to measure the volume dependence on the composition and determining the slope of the dV / dn on the composition of the known (Atkins, 1994).

Molal molal volume and entropy is always positive, but the corresponding partial molal quantity need not be. For example, the partial molal volume limit of MgSO 4 (partial molal volume in the limit of zero concentration is -1.4 cm 3 / mol), which means the addition of 1 mol of MgSO 4 into the large volume of water that produces the decrease in volume of 1.4 cm 3. Depreciation occurs because the salt was decided that the open structure of water when hydrated ions so that the volume is slightly shrunk (Atkins, 1994).

Density of the substance is not a fixed quantity, but varies depending on the pressure and temperature when the measurement. For some substances (especially gases and liquids), the volume will be more easily measured than its mass, and if rapatannya known to the conversion factor between volume and mass can be obtained. By knowing the density and molar mass of a substance, we can easily calculate the molal volume, ie volume occupied by one mole of substance.

Vm = = Molar volume (cm 3 mol -1)(Oxtoby et al, 2001).

Behave in an ideal system with all the thermodynamic relations derived by this model. Because it's from ideal behavior, the thermodynamic relations derived can be described in two parts, namely:
Partial molal quantities, such as the partial molal volume, enthalpy, and so forth.
Activity and activity coefficient, the application of Debye-Huckel limiting law.

There are three main partial molal thermodynamic properties, namely:
Partial molal volume of the components in solution.
Partial molal enthalpy (also referred to as the differential heat of solution).
Partial molal free energy (called the chemical potential).

Partial molal volume of the components of a mixture changes depending on the composition, because each type of molecular environmental changes if the molecular composition changed from pure A to B pure. Molecular environmental changes and changes in the forces acting between molecules is what produces the variation of thermodynamic properties of the mixture if the composition changed. Partial molal volume of water and ethanol throughout full range of composition, at a temperature of 25 ˚ C. once we know the partial molal volume of water and ethanol or a mixture of these two particular composition, we can determine its properties (and Dogra Dogra, 1990).

The total volume of solution containing 1000 grams (55.51 moles) of water and m moles of solute is given by the equation

V = N 1 V 1 + N 2 V 2 = 55.51 V 1 + mV 2 (1)

Suppose V 1 o is a pure volumemolalair (V 1 o = 18.016 / 0.997044 = 18.069 cm 3 at 25 °), the molal volume of solution (ф) is defined as follows:

V = N 1 V 1 O + N 2 V 2 = 55.51 V 1 o + Mф (2)

or

ф = (3)

unknown

V = (4)

Where d: density of solution

d o: density of pure solvent

N 2: molecular weight solutes

Thus obtained:

ф = (5)

ф = (6)

Where W e: weight empty piknometer

W o: weight piknometer containing pure water

W: weight piknometer containing solution

(Taba and Fauziah, 2006).

Partial molal Quantities tell us how the properties of solutions change with concentration. We need to know the partial molal Quantities for all the extensive properties of a solution, including V, G, H, S, and A. For example, the partial molal volume is Important in Oceanography and aquaticenvironmental science, Which Is Why We Measure the partial molal volume of NaCl solutions in this lab. That is another example of partial molal volume is needed for careful Calculations in Biochemistry of the molecular weights of proteins and nucleic acids using ultracentrifugation (Atkins, 1994).

Number of partial molal us how the properties change with the concentration of the solution. We need to know the amount of partial molal for all extensive properties of solutions, including the V, G, H, S, and A. For example, the partial molal volume is important in oceanography and marine environmental science, which is why we measure the partial molal volume of NaCl solution at this laboratory. Another example is that the partial molal volume is needed in biochemistry for careful calculation of molecular weight of proteins and nucleic acids using ultracentrifugation (Atkins, 1994).

There are three main partial molal thermodynamic properties, namely

(A) The partial molal volume of the components in the solution

(B) partial molal enthalpy (also called heat differential)

(C) The partial molal free energy (chemical potential)

These qualities were obtained with the help of (a) graphical method, (b) using the relationship analitikyang shows the relationship J and n i, and (c) using a function called real molal scale which is determined as:

ф J i = (7)

where J i n is the molal price for pure components, and using interseft. One thing to remember is that the partial molal properties of a component in a solution, and molal properties for pure compounds is the same as if the solution is ideal (Dogra and Dogra, 1990).

Calculation of partial molal can transactions are carried out in several ways, namely:
Graph Method

In this method, the value of J plotted as a function of composition composition solution by keeping all other components and equipment, except one. If the plot is linear, the slope of the line will be a partial molal quantity of that component. It also shows that the partial molal properties of these components is also not dependent on the concentration. If the plot in this case is not linear, then:

J i = n → 0 (8)

(Dogra and Dogra, 1990)

Analytical Methods
If extensive price can be expressed as an algebraic function of these compositions, the partial molal properties can be computed in anallitik (Dogra and Dogra, 1990).

Sodium is a soft silver-white metal, which melted at a temperature of 97.5 ° C. Sodium rapidly oxidized in moist air, it must be kept entirely submerged in the solvent naphtha or xylene. This metal reacts violently with water, forming sodium hydroxide, and hydrogen:

2Na + 2H 2 O → 2Na + + 2OH - + H 2 ↑

CHAPTER III
EXPERIMENT METHOD

3.1 Materials

The materials used in them is 3 M NaCl, distilled water, paper labels, and the tissue roll.
Experiment Equipment

3.2 Tools

The tools used in this experiment is to squash them drinks 100 mL, 500 mL beaker, piknometer, analytical balance, pumpkin spray, pipette 50 mL volume, volume of 10 mL pipettes, pipettes volume 5 mL, bulb and pipette drops.

3.3 Experimental Procedure

3 M NaCl was diluted so that its concentration becomes and times the concentration originally by way memipet mother liquor (NaCl 3 M) were 25 mL for the concentration of 1.5 M and 12.5 mL for the concentration of 0.75 M. As for the concentration of 0.375 M NaCl 1.5 M was taken as much as 12.5 mL of 0.1875 M and for the concentration of 0.75 M NaCl was taken as much as 12.5 mL, then all the solution is diluted in a pumpkin drinks to mark the boundary with distilled water.
Empty Pikno clean, dry and weighed.
Piknometer filled with distilled water and then closed tightly and the outer layer was dried using a towel roll and then weighed.
Piknometer replaced with distilled water in 3 M NaCl, 1.5 M, 0.75 M, 0.375 M; and 0.1875 M. every turn of the solution, it must be rinsed piknometer repeatedly with a solution that will be used.
Recorded at room temperature.

CHAPTER IV
RESULTS AND DISCUSSION

4.3 Discussion

Through this experiment we can determine the molal volume of NaCl as a function of concentration by measuring the density of the solution. Solution density measurements carried out using piknometer.

In this experiment, NaCl was used as a material which will be determined the value of its partial molal volume in various concentrations. Dilution carried out to determine how the relationship with a large concentration of a solution of the partial molal volume. 3 M NaCl was used diluted into and from the original concentration. In addition to the concentration, density can also affect the partial molal volume. As for room temperature recording done in order to obtain the density of the solution.

Density measurements performed using piknometer. Measurement is done by weighing the empty and piknometer piknometer containing sample solution first. Piknometer empty weighing is done as a comparison. In order not to affect the results of measurements, piknometer used should be in a state of absolutely dry. Similarly, while changing the NaCl solution in different concentrations, piknometer should be cleaned and rinsed the inside with a solution that will be used. This needs to be done so that the solution to be measured density is not contaminated with other substances.

From this experiment, the obtained solution molal volume ( ) 3 M NaCl at 32.3953 , 1.5 M NaCl at 24.0522 , 0.75 M NaCl at 23.7124 , 0.375 M NaCl at 23.6374 , And NaCl at 23.5077 0.1875 .

Partial molal volume is the volume expansion that occurs when 1 mole of component I added to a solution. The result is negative, ie

The value of the partial molal volume showed a negative value, meaning the event of termination bonding solution, which occurred in this experiment is to break the bond between the ions Na + and Cl - ion. Where merupkan NaCl initially, then changed to the constituent ions, namely Na + and Cl -.

CHAPTER V
CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusion

From the experiments obtained slope value of 20.687 .

5.2 Suggestions

More assistants should oversee the workings praktikan and explain in more detail. Experiments carried out should also be used in various types of other substances in the determination of partial molal volume so that we can compare between the materials to each other value of the partial molal volume.

REFERENCES

Atkins, PW, 1994, Chemical Physics, grants, Jakarta.

Atkins, PW, Physical Chemistry, 7th Ed, Section 7.1, grants, Jakarta.

Dogra, SK, and Dogra, S., 1990, Physical and Chemical Problems, Penenrbit University of Indonesia, Jakarta.

Oxtoby, DW, Gillis, HP and Nachtriebe, NH, 2001, Principles of Modern Chemistry, grants, Jakarta.

Of view, Tuntung., Monday, 07 December 2009.

Taba, P., and Paulina, St., 2006, Practical Guide of Physical Chemistry, Physical Chemistry Laboratory Science, State UH, Makassar.

Thermochemistry

CHAPTER I
INTRODUCTION

1.1 Background

In our daily lives, we whose names are not spared from the heat or the heat. Heat is a lot we need good daam our lives when we were cooking, drying and many more. In the world of science known as thermodynamics terms. Science is one of the various branches of science that studies about the heat or the heat itself, work and other forms of energy, with the equilibrium in chemical reactions and in changing circumstances. Thermochemistry here is very closely related in terms of thermodynamics which handles the measurement and interpretation of the results of heat changes that accompany chemical reactions and changes in circumstances which happen.

In general, any chemical reaction involving gases, whether in reaction to the formation (synthesis) and the termination reaction. Generally, heat linkage here is not only necessary but also is released. Any chemical reaction that requires as a condition of the reaction heat is called endothermic reaction, while all chemical reaction that releases heat at the time of reaction is called exothermic reactions. The tool used in measuring the heat is called the calorimeter.

In the lab, we can make a calorimeter that is by using a large beaker in the glass and then we put the cork. And to measure the heat from a sample, we simply put it into a small beaker and beaker are then inserted into a large glass earlier. The remaining space and then filled with insulating material. Then by using a thermometer, the temperature of solution can be measured.

Based on the above theory, this time, we perform experiments to determine the calorimeter constant and heat of neutralization in a solution by using a calorimeter.

1.2 Experiment Objectives

1.2.1 Purpose Experiment

Know and study the calorimeter constant and heat calorimetrically neutralization.

1.2.2 Experiment objectives

Calorimetrically determine the calorimeter constant.
Determine the neutralization heat of a reaction of HCl by NaOH neutralization calorimetrically.

1.3 Principle Experiment

In determining the constant of the calorimeter, mixed with distilled water, distilled water is heated and then measured the temperature at a certain time interval. In determining the heat of neutralization, acid reacting with the alkaline solution and measured the temperature at half minute intervals for 5 minutes. With the addition of methyl orange as an indicator of neutralization reaction perfectly.

CHAPTER II
LITERATURE REVIEW

The system is part of the universe that we learn. Maybe the system is an ongoing chemical reaction in the beaker. Outside of the system is called the environment and can also be said that the environment is part of the universe which limits the system. The system can be classified in an open system, closed, adiabatic system and isolated system.
Open systems are systems where for the system can undergo a process of exchange of matter and heat.
Closed system is a system that did not change during the process, but can occur and the environmental heat exchange.
Isolated system is a system that can not be held either in the form of interaction between heat, work or materials, or materials with the environment.
Adiabatic system is a system during a process can not perform the exchange of heat with its surroundings (Respati, 1986).

Thermochemistry is the branch of chemistry relating to the reciprocal relationship of heat with chemical reactions or physical condition changes. In general, Thermochemistry is the application of thermodynamics to chemistry. Thermochemistry is the synonym of chemical thermodynamics (Klotz, 1950).

Heat of reaction can be expressed as a change in energy products and reactants at constant volume (ΔE) or at constant pressure (ΔH). Price volume constant (ΔE) is obtained when the reaction is performed in a bomb calorimeter, ie at constant volume in a glass cup or pumpkin isolated, thermos bottles, and others. Because the detailed process properly, then the heat released or absorbed only state functions, among others, Q p = (ΔH) or Q v = (ΔE) on the functioning of the state. A desired chemical reaction can be written as a series of many chemical reactions. If someone knows the heat of reaction of each stage can be calculated by adding or reducing the thermal reaction. This principle is where the heat of reaction was added or subtracted algebraically called Hess's law (Dogra and Dogra, 1990).

Energy change is so far arising from the direct mechanical work to heat the system or the occurrence of contact between the two systems at different temperatures. In chemistry, a source of change in an important additional energy comes from heat that is given or taken away from the path of a chemical reaction (Oxtoby, 2001).

Hess said that all the heat from a chemical reaction, at constant pressure is the same, regardless of the course of the reaction, so the Δ H for a reaction depends only on the initial and final state only (Respati, 1986).

In general, the chemical reaction is accompanied by thermal effects; the exothermic reaction heat is released, whereas the endothermic reaction heat is absorbed. Amount of heat associated with a reaction depends on the type of reaction, the amount of substance that reacts, in the physical state of these substances and the results of the reaction reagent, and on temperature. Experimentally determined reaction heat with the calorimeter (Taba, and Fauziah., 2006).

Calorimeter used to measure heat changes that occur in chemical reactions the reaction is generally conducted in a place that diisoler. Changes in temperature were measured with a sensitive thermometer. The result of multiplication between temperature and total heat capacity of water and the calorimeter, is a measure of hot dri happened. His best when the reaction can take place quickly, so that cooling can be made a minimum and the reaction is complete. Water in the calorimeter must be stirred, so that temperature becomes uneven, but the heat caused by this mixing should be as small as possible, also the heat loss due to evaporation of water must be made a nicety. To prevent heat radiation, the walls are made double and divakumkan calorimeter (Respati, 1986).

Heat of reaction at a certain temperature, T, is the heat released or absorbed, if the number of substances reactant at temperature T, was transformed into reaction products at the same temperature. If the reaction takes place in an adiabatic calorimeter nature, there will be changes in the temperature of the reaction mixture. For example, reaction between reagent-reagent A and B, which was originally located at temperature T, yielding the product AB at temperature T, to determine the heat of reaction at temperature T, note the following scheme:

A (T) + B (T) AB (T ')

AB (T)

Under this scheme can be derived, ΔH = 0 = ΔH + ΔH ', so that ΔH =-ΔH''=-C (T' - T), with C is the heat capacity of calorimeter and contents. C, stating the amount of heat necessary to raise the temperature of one degree calorimeter and its contents. If the mass is m and the reaction mixture calorific capacity C p, then C = C p + W, with W is called the constant of the calorimeter or calorimeter water value, ie the amount of heat to raise the temperature of the calorimeter and other equipment (thermometer, stirrer, etc.) as much as 1 o C. A total of V cm 3 of water is inserted into the calorimeter and after reaching the thermal equilibrium temperature (T = 1). Then added V cm 3 of water at higher temperatures (= T 2). If the final temperature is T a system, the heat released by the VC H2O is hot water (T 2 - T a); C H2O is the heat capacity of water per gram; with water mass is taken equal to 1 g / cm 3. heat received by the water in the calorimeter and the calorimeter itself is

VC H2O (T a - T 1) + W (T a - T 1)

Thus,

VC H2O (T 2 - T a) = VC H2O (T 2 - T a) + (T a - T 1)

Thus,

T 1 + T 2 - 2T a

W = VC H2O

T a - T 1

(Taba and Fauziah., 2006).

In the heat of neutralization, V cm 3 of acid solution, with a particular concentration, placed in the calorimeter, then added V cm 3 bases with the same concentration. If the temperature of the two solutions before the mixed remains the same, namely T, and the final temperature is T ', then the heat of neutralization, ΔH T, can be calculated from the expression

ΔH T = - (4.2 m + W) (T '- T)

with m is the mass of solution and W is the constant of the calorimeter. Usually the neutralization heat (such as heat of reaction in general) is expressed per mole of acidic or alkaline. To this the result of the above calculation must be multiplied by 1000/VM, with M is kemolaran solution (Taba and Fauziah., 2006).

CHAPTER III
EXPERIMENT METHOD

3.1 Materials

The materials used in these experiments was 1 M NaOH, 1 M HCl solution, methyl orange indicator solution, insulating materials of plastic pieces, distilled water, and cork

3.2 Equipment

The equipment used was 2000 mL beaker, 250 ml beaker, thermometer scale of 100 o C 0.1 o C, stopwatch, stirrer circumference, burners, measuring cups 100 mL, 50 mL burette, stative, and pipette drops.

3.3 Experimental Procedure

3.3.1 Determination Calorimeter Constant

1. Compiled calorimeter tools like the image

Figure Calorimeters

2. Entered into the distilled water as much as 100 mL beaker and put in the calorimeter were then allowed some time to reach thermal equilibrium. Her temperature was measured with a thermometer and recorded as T 1.

3. Distilled water put into another beaker of 100 mL and heated in the heater until the temperature of 50 o C, and temperatures were recorded as T 2.

4. Distilled water that has been heated (temperature 50 o C) and then inserted into the calorimeter containing cold distilled water which had been provided previously. When distilled water is poured, the stopwatch is running and then measured and recorded the temperature using a thermometer in the solution of a half-minute intervals for five minutes.

3.3.2 Determination of Heat of neutralization.

1. 1 M NaOH solution is left as many as 100 mL, 100 mL 1M HCl solution at room temperature for some time until the two solutions have the same temperature. Then the recorded temperature (T)

2. Acid solution is inserted into the calorimeter.

3. Alkaline solution is poured into the acid solution before, and quickly closed calorimeter. Along with poured alkaline solution, the stopwatch starts.

4. Stirring, slowly, the temperature is recorded every half minute for five minutes.

5. Add 2-3 drops of methyl orange indicator solution to determine whether there has been a perfect neutralization. If the excess acid solution then titrated with a base, but if the excess base was titrated with acid.

CHAPTER IV
RESULTS AND DISCUSSION

4.3 Discussion

At this time the thermochemical experiment used a simple calorimeter equipment. In this calorimeter we attach cork and on the sides paired with insulating material consisting of plastic scraps. This bertujan to the possibility of a large heat exchange can be minimized. This means that the character of an adiabatic calorimeter used ie no heat exchange occurs between the system and environment.

In determining the constant of the calorimeter used water as a main ingredient. In determining the constant of the calorimeter will be two water treatment where as many as 100 mL and left at room temperature as much as 100 mL heated. This is aimed to know the temperature of the mixing process. And from these we can know the temperature constant kalorimeternya using the existing formula.

As at the time of mixing, stirrer circumference is used to stir the water mixture to mix well and using the thermometer, we can measure the temperature. The temperature measurement is done every half a minute for five minutes. This is intended so that we can control the temperature changes that occur every half minute. And from data obtained in the first high temperature will drop over time, and when analyzed by the graph obtained by the point or the final temperature of 311.4 K. The calorimeter constant value (W) obtained namely equal to 210 J / K.

In determining the heat of neutralization (ΔH T) used a strong acid solution that is namely HCl and NaOH strong base. In determining these values we first equalize the temperature between the two solutions, it is intended to allow an equilibrium between acid and alkaline solution is used. Mixing the two solutions was done quickly and then stirred with a mixer to mix well in circumference with a measured temperature. The range of temperature measurement time is the same mix when deciding on the range of time constant of the calorimeter yaknis every half minute for five minutes. And from the measurement results obtained in terms of graphs which declined at mixed temperatures are quite different from the initial temperature of each solution in which the initial temperature obtained during the mixing namely equal to 307.5 K and the final temperature of 307.1 K. The graph obtained from analysis of the final temperature of 307.1 K. sbesar system After the temperature measurement is carried out tests of whether it is neutral solution and after adding a few drops of methyl orange indicator solution turned pink. This neutralization membukikan that occurred on this mixing. The calorific value is obtained based on the results of neutralization experiments namely equal to +5.32 kJ / mol. Positive values indicate that the reactions that take place are endothermic reactions or in terms of heat transfer occurs.

The results obtained are compared with existing values in the literature in which the neutralization heat of -55.90 kJ / mol, we can see that there is quite a big difference. This is because these two solutions were mixed after a mixed indirect and also because the scale of the thermometer readings are not accurate.

CHAPTER V
CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusion

From the experiments have been conducted, it can be concluded, among other

1. Calorimeter constant (W) is 210 J / K

2. Heat of neutralization (ΔH T) is + 5.32 kJ / mol

5.2 Suggestions

The advice I can give based on this experiment, ie, other materials should be used to calculate the heat Compound neutralization eg weak acid and weak base.

REFERENCES

Dogra, S., and Dogra, SK, 1990, Physics and Chemistry Problem Solved, UI-Press, Jakarta.

Klotz, I. (1950). Chemical thermodynamics (textbook). New York: Prentice-Hall, Inc.

Oxtoby. 2001. Principles of Modern Chemistry. Grants. Jakarta.Rivai, H., 1995, Principle of Chemical Examination, UI-Press, Jakarta

Respati, 1986, Chemistry for Universities, New Literacy, Jakarta.

Taba, P., and Fauziah, St., 2006, Practical Guide of Physical Chemistry, Laboratory of Physical Chemistry, Faculty of Mathematics and Natural Sciences, Hasanuddin University, Makassar.