Exp-03-process.docx

Shahjalal University of Science and Technology, Sylhet Dept. of Chemical Engineering and Polymer Science Lab report On Experiment name: Study the distribution of Benzoic Acid between Benzene and Water at room temperature and hence show that Benzoic acid dime rises in Benzene Course Code: CEP-352 Submitted To: Md Zakir Hossain Associate Professor Dept. of CEP, SUST Submitted By: Lab group-01 Registration Number 2016332002 2016332004 2016332010 2016332014 2016332023 2016332034 2016332039 Date of Submission:04-03-2019

Taslima Islam Nadi Salma Fariha Khan Mahazabin Mim Kashfia Nehrin Shreya Roy Al Mahmud Arjan Saha

Table of Contents Theory: .......................................................................................................................................................... 3 Introduction .................................................................................................................................................. 5 Objective ....................................................................................................................................................... 5 Result and calculation: .................................................................................................................................. 6 Discussion: .................................................................................................................................................... 8 Remarks and Comments: .............................................................................................................................. 8

Theory: When a solute is shaken with two solvents which are immiscible with each other but in both of which the soluble, then the solute is found to distributed itself between the two solvent in such a way that the ratio of the concentration of the solute in the solvent is constant at a constant temperature. If C1 and C2 are the concentration of the solute in solvent 1 and 2 respectively, then according to the Nernst distillation law: C1/C2 = KD The constant KD is called the distribution coefficient or distribution ratio. The distribution law is valid when the molecular species of the solute in the two solvents remain the same, i.e., there is no association or dissociation of the solute in any of the solvents. If the solute undergoes association in one of the solvents but remains unchanged in the other solvent as shown in the figure, the law can not be applicable as such since the molecular species have under zone a change. Using the law of mass action can do modification for this. Considering the equilibrium between the different molecular species A undergoing association in the solvents. The following reaction can easily obtain: nA  (A)n C3

C2

C2/(C3)n = Kꞌ [mass law constant] (n√C2)/C3 = constant……………….(1) Again, C1/C2 = constant…………………(2) Dividing equation (2) by (1) we get, (C1/C3)/(n√C2√C3) = constant  C1/(n√C2) = constant…………….(3) Benzoic acid exit dimmer in benzene solution. Thus, distribution low can be used for ascertaining molecular association. From equation (3) we get, C1/(n√C2) = K constant logC1 = (1/n) logC2 + log K

nA - (A)n C3

solvent 2

C2

Solvent 1

C1 No change

Figure: Molecular association in one solvent. If we plot a graph of log C1 versus log C2, we get a straight line passing through Y-axis from the slop of the curve we can calculate the value of n and from the intercept the value of K. The dissociation of benzoic acid in the aqueous phase being small, so neglected.

Log C1 Slope = 1/n

Log K

Log C2

Equipment and chemicals required: Four glass stopper bottles, a large beaker, pipettes (5ml & 10ml), benzoic acid, benzene, NaOH of 0.1 & 0.01 M, phenolphthalein, burette, shaking machine.

Introduction: When a solute is shaken with two immiscible solvents, it gets distributed between the solvents. This distribution of solute in two solvents depends upon the solubility of the solute in two solvents. At the distribution equilibrium, the ratio of concentration of the solute in the two solvents is constant at a given temperature. The constant is called the partition co efficient (K) or the distribution coefficient of the solute between two solvents.1 In the physical sciences, a partition coefficient or distribution coefficient is the ratio of concentrations of a compound in a mixture of two immiscible phases at equilibrium. This ratio is therefore a measure of the difference in solubility of the compound in these two phases. The partition coefficient generally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized). In the chemical and pharmaceutical sciences, both phases usually are solvents. Most commonly, one of the solvents is water, while the second is hydrophobic, Hence the partition coefficient measures how hydrophilic ("water-loving") or hydrophobic ("water-fearing") a chemical substance is.2 Earlier The partition coefficient was known as distribution ratio.The first study of partition coefficient was performed by Berthelotand Jungfleisch and came to result that the ratio of concentration of solute is constant and doesnot depend on solvent volume.But Nernst have proved that partition coefficient remains constant if single type of solute is used.It is the activity of solute to enter in organic phase or aqueous phase which is explained by Partition Law by taking benzoic acid in benzene and water,which explained that benzoic acid exist in dimeric form.3 Partition coefficients can be measured experimentally in various ways (by shake-flask, HPLC, etc.) or estimated by calculation based on a variety of methods (fragment-based, atom-based, etc.).

Objective: To determine the distribution coefficient of benzoic acid between benzene and water.

1 2 3

https://labmonk.com/partition-co-efficient-of-benzoic-acid-in-benzene-and-water https://www.google.com/search?client=firefox-b-d&q=distribution+coefficient+of+benzoic+zcid

https://www.ripublication.com/ijcher16/ijcherv8n1_04.pdf?fbclid=IwAR0vaPIRWLUfWoJwBhPASP7DN89Lr2dsPHL92rnH6Gsv_h4chNF6S3T6Xw

Result and calculation:  Analysis of benzene layer: Bottle no

01 02 03 04

Volume of Benzene layer, ml 5 5 5 5

Volume of 0.1M NaOH 1 2 3 8.5 8.7 8.9 17.1 16.5 16 15.5 16.5 14.4 26.7 25.6 27

Average volume 8.7 16.53 15.4 26.43

Conc. Of Benzene layer, Cor 0.087 0.165 0.154 0.2643

Average volume, ml 10.7 20 15.97 24.73

Conc. Of aqueous layer, Caq .00535 .01 .00798 .01236

 Analysis of Aqueous layer: Bottle No

01 02 03 04

Volume of Aqueous layer, ml 10 10 10 10

Volume of 0.1M NaOH 1 2 3 10.4 10.7 11 20.5 19.5 20 15.4 17.5 15 24.5 25 24.7

 Evaluation of Cor/Caq : Bottle no.

01 02 03 04

Conc. Of Organic layer Cor 0.087 0.165 0.154 0.2643

Log Cor

-1.06048 -0.78252 -0.81248 -0.5779

Conc. Of aqueous layer Caq .00535 .01 .00798 .01236

Log Caq

Cor/Caq

-2.27165 -2 -2.098 -1.90798

16.26168 16.5 19.29825 21.3835

A plot of log Caq against log Cor is given below:

0 -1.2

-1

-0.8

-0.6

-0.4

-0.2

0

Log Caq

-0.5 y = 0.7677x - 1.4488

-1 -1.5 -2

Log Cor

-2.5

From the graph, the equation is: y= 0.7677x – 1.4488 Comparing this equation with Log Caq = 1/n Log Cor + Log k The slope: 1/n = 0.7677 → n = 1.30 And the intercept: Log k = -1.4488 → K = 2.34 × 10-2

Result: 1. The distribution coefficient of Benzoic Acid between two solvents Benzene and Water is: K =2.34 × 10-2 2. So, it can be said that the benzoic acid is diereses in Benzene.

Discussion: The experiment was carried out to study the distribution of benzoic acid between benzene and water. The value of constant K and n was determined by the experiment. Four samples of benzoic acid; 1,2,3 and 4gm were taken in 4 individual bottles. Each of which was carried under the experiment to obtain concentrations of benzoic acid in water (Caq) and pure benzene (Corg). the ratios of (Corg/Caq ) for 4 samples of 1,2,3, and 4 gm benzoic acid, evaluated were 16.26168, 16.5, 19.29825 and 21.3835 respectively. A plot was established by placing log (Caq ) against log(Corg ) using the tabulated values. From the figure, it can be seen that the resultant curve is a straight line. The slope of which is 1/n and Y-intercept is log(K). The value of n evaluated was 1.30 and that of distribution coefficient K between benzene and water was 2.34 × 10 -2. This value actually shows that benzoic acid undergone association in benzene solvent, consequently forming dimmer of benzoic acid. The experiment was carried under the control of some significant conditions (Constant temperature, Non-miscibility of solvents, same molecular state)

Remarks and Comments: Some deviated (in small extent) value can be seen in the obtained plot for 4 samples. Constant temperature maintaining was one of the most significant pre-condition for this. Along this condition some other criterion also could not match perfectly due to absence of proper and a developed laboratory. But still, result that is obtained was nearly approximate close to real value which was satisfactory.