DETERMINATION OF PERCENTAGE COMPOSITION OF UNKNOWN SOLUTION BY USING REFACTOMETER
AIM : To determine the percentage composition of unknown solution by using refractometer
REQUIREMENTS : Carbon tetra chloride (CCl4), Benzene, Xylene, Pipette, Beaker,
Abbeys Refractometer.
PRINCIPLE :
when a ray of light beam passes from one medium to another, it shows refraction i.e., changes in the path. If it passes from rarer to denser medium. Eg: air to water, it bends towards the normal, angle of incidence ‘i’ is more than the angle of refraction ‘r’ . According to snells law the refractive index ‘n’ of second media with respect to first is
η = sin i
Sin r
The velocity of light decreases when it passes through a denser medium. Hence the ratio in the equation may be written as the ratio of the velocities of light in two media.
η = velocity of light in vacuum
Velocity of light in medium
RI is greater than 1 for the substances denser than air because the velocity of light in air is always higher when compared to the value in denominator, liquids and mixture of liquids passes a characteristic refractive index, it is common physical and chemical properties of a liquid. Eg: CCl4 has low refractive index because of its interaction with light to delocalize to P-cloud..
RI of the mixture satisfies the algebraic sum of refractive index of individual components. When benzene is added to CCl4 the RI is increases so the proportion of benzene is linear. RI is taken on Y-axis and Percentage volumetric compositon of Benzene in CCl4 is taken on X-axis, Plotting the points gives a straight line. Liquids will form binary mixtures i.e., which are miscible in all proportions, which can be employed for this purpose.
The principle explained above is used to find % composition of Benzene in CCl4. RI of unknown liquid is determined experimentally % V/V of benzene in CCl4 of unknown mixtures can be obtained from the graph.
Factors influencing RI :
• RI varies with the wavelength and temperature.
• It is represented by n20. This symbol indicates that the RI has been determined at 200C using D line emission of Sodium (Na) at 589nm.
• Abbeys refractometer is commonly used to determine the refractive index.
Applications:
RI is used in
1. Substances can be identified.
2. Purity of the substances can be measured.
3. Concentration of one substances dissolved in another liquid can be determined.
4. Molar refraction Rm is used to predict structural features of the molecules. Rm can be calculated from refractive index values.
5. Dielectric constant and molar polarizability can be obtained from refractive index.
PROCEDURE :
1. Determine RI of CCl4.
2. Prepare solutions of Benzene in CCl4 by taking different proportions of Benzene.
3. Draw a graph by taking ‘n’ value on y-axis and % concentration on x-axis.
4. Determine RI of unknown sample.
5. Determine concentration of unknown sample from the graph.
REPORT: The concentration of unknown sample of CCl4 by using Abeys Refractometer was
found to be ________ .
S.No CCl4 volume in ml Benzene volume in ml % composition of benzene in CCl4 Refractive index
DETERMINATION OF PERCENTAGE COMPOSITION OF UNKNOWN SOLUTION BY USING REFACTOMETER
AIM : To determine the percentage composition of unknown solution by using refractometer
REQUIREMENTS : Carbon tetra chloride (CCl4), Benzene, Xylene, Pipette, Beaker,
Abbeys Refractometer.
PRINCIPLE :
when a ray of light beam passes from one medium to another, it shows refraction i.e., changes in the path. If it passes from rarer to denser medium. Eg: air to water, it bends towards the normal, angle of incidence ‘i’ is more than the angle of refraction ‘r’ . According to snells law the refractive index ‘n’ of second media with respect to first is
η = sin i
Sin r
The velocity of light decreases when it passes through a denser medium. Hence the ratio in the equation may be written as the ratio of the velocities of light in two media.
η = velocity of light in vacuum
Velocity of light in medium
RI is greater than 1 for the substances denser than air because the velocity of light in air is always higher when compared to the value in denominator, liquids and mixture of liquids passes a characteristic refractive index, it is common physical and chemical properties of a liquid. Eg: CCl4 has low refractive index because of its interaction with light to delocalize to P-cloud..
RI of the mixture satisfies the algebraic sum of refractive index of individual components. When benzene is added to CCl4 the RI is increases so the proportion of benzene is linear. RI is taken on Y-axis and Percentage volumetric compositon of Benzene in CCl4 is taken on X-axis, Plotting the points gives a straight line. Liquids will form binary mixtures i.e., which are miscible in all proportions, which can be employed for this purpose.
The principle explained above is used to find % composition of Benzene in CCl4. RI of unknown liquid is determined experimentally % V/V of benzene in CCl4 of unknown mixtures can be obtained from the graph.
Factors influencing RI :
· RI varies with the wavelength and temperature.
· It is represented by n20. This symbol indicates that the RI has been determined at 200C using D line emission of Sodium (Na) at 589nm.
· Abbeys refractometer is commonly used to determine the refractive index.
Applications:
RI is used in
1. Substances can be identified.
2. Purity of the substances can be measured.
3. Concentration of one substances dissolved in another liquid can be determined.
4. Molar refraction Rm is used to predict structural features of the molecules. Rm can be calculated from refractive index values.
5. Dielectric constant and molar polarizability can be obtained from refractive index.
PROCEDURE :
1. Determine RI of CCl4.
2. Prepare solutions of Benzene in CCl4 by taking different proportions of Benzene.
3. Draw a graph by taking ‘n’ value on y-axis and % concentration on x-axis.
4. Determine RI of unknown sample.
5. Determine concentration of unknown sample from the graph.
REPORT: The concentration of unknown sample of CCl4 by using Abeys Refractometer was
found to be ________ .
S.No | CCl4 volume in ml | Benzene volume in ml | % composition of benzene in CCl4 | Refractive index |
|
|
|
|
|
DETERMINATION OF SURFACE TENSION OF LIQUID USING DROP COUNT METHOD
AIM:- To determine the surface tension of the given liquid by drop count method using stalagmometer at room temperature
REQUIREMENTS:-stalagmometer, sample solution, acetone & water
PRINCIPLE:- Surface tension is defined as the force acting in dynes acting at right angles to the surface of liquid along 1 cm length of the surface . units of surface tensions is dynes/cm the magnitude of the surface tension is the measure of strength of intra molecular attractive forces there are two forces determining surface tension of liquids .
They are 1.Drop weight method
2.Drop count method by capillary method.
Drop method is convenient and quick for this stalagmometer is used .surface tension measure the strength of cohesive forces of liquid. For example water has strong cohesive forces so surface tension is more on water other hand liquid such as benzene, have weak cohesive forces and have low surface tension when compared to water. The lower the surface tension of the liquid the small of the size of the drop formed. Then more number of drops of found for the same volume of the liquid. Hence simply counting the number of drops for an unknown liquid and water is sufficient to calculate the surface tension.
PROCEDURE:
1. Clean the stalagmometer with distilled water and acetone and dry using hot air drier.
2. Fits the stalagmometer to a stand in a vertical position.
3. Dip the stalagmometer in a beaker of water (H2O) and suck the water upto level higher than the position of the mark.
4. Let the water flow down and count the number of drops passing between the upper and lower mark.Repeat the experiment thrice to get the number of drops be n1.
5. Remove water, clean, dry and repeat the procedure with the given liquid in the same manner thrice. Let the number of drops be n2.
REPORT :
The surface tension of the given liquid by drop count method using stalagmometer was found to be ______________ dyne/cm.
S.No | NUMBER OF DROPS OF |
WATER | SAMPLE SOLUTION |
|
|
|
DETERMINATION OF SURFACE TENSION OF LIQUID USING DROP WEIGHT METHOD
AIM:- To determine the surface tension of the given liquid by drop weight method using stalagmometer at room temperature
REQUIREMENTS:-stalagmometer, sample solution, acetone & water, sample weighing bottle.
PRINCIPLE:-
When a liquid is allowed to flow it form drops which increase in size from, it form drops which increase in size from the tip of the tube. The weight of the drop of a liquid is equal to the surface tension at the circumference of the tube.
PROCEDURE:
1. Select a clean stalagmometer wash it with distilled water and acetone and dry using hot air drier.
2. Dip the stalagmometer in a beaker of water (H2O) and suck the water up to the upper mark A.
3. Fits the stalagmometer to a stand in a vertical position.
4. The liquid is allowed to flow to mark B and drops of liquid are collected in free air beaker.
5. Repeat the experiment with water and weigh the drops of water formed between a fixed volume ( mark A-B).
6. The surface tension is found using the equation
7. Remove water, clean, dry and repeat the procedure with the given liquid in the same manner thrice. Let the number of drops be n2.
REPORT :
The surface tension of the given liquid by drop weight method using stalagmometer was found to be ______________ dyne/cm.
DETERMINATION OF THE POROSITY OF THE GIVEN POWDER
AIM: To determine the porosity of the given powder.
PRINCIPLE :
Suppose a powder is placed in a graduated cylinder and the total volume is noted the volume occupied in the cylinder is known as ‘Bulk Volume’ Vb.
If the powder is known porous i.e., thus no internal forces and capillary spaces, the bulk volume of the powder consist of true volume of the solid particles and the volume of space between the particles. The volume occupied by the spaces is known as ‘Avoid Volume’.
Vb = V+Vt
V=Vb-Vt
The porosity of the powder is defined as ratio of wide volume to the bulk volume.
€=Vb-Vt
Vb
The porosity frequently expressed in percentage porosity = € X 100
PROCEDURE :
1. Weigh 50gm of Calcium carbonate and starch and pass in a graduated cylinder.
2. Note the volume initially occupied by the sample as Vb.
3. Top the cylinder under constant time intervals and note the volume. After 50,100,200,300,,, tappings.
4. At one stage we recognize the volume occupied is same after several tapings and the volume does in change on again taping also.
5. Note the volume as true volume Vt.
6. Porosity can be calculated by using the equation
7. The noted readings then added to calibrated value gives the actual value. Repeat the procedure for different samples.
€=Vb-Vt
Vb
REPORT:
S.No | Name of the sample | Bulk Volume | No.of Tappings | True volume | Pure Volume | %porosity |
|
|
|
|
|
|
|
DETERMINATION OF UNKNOWN CONCENTRATION OF NaCl SOLUTION USING CRITICAL SOLUTION TEMPERATURE
AIM: To determine the concentration of NaCl in a given solution using Critical Solution Temperature Method.
THEORY: Addition of substance to a partially miscible two liquids produces a system which contains three components. If the added material is soluble in only one of two liquids, the mutual solubility of the liquid phase is decreased. If the original solution as an upper critical solution temperature. The temperature is raised. Addition of naphthalene to a mixture of phenol and water results in an increase in the critical solution temperature. Since naphthalene is soluble only phenol, likewise, there is an increase critical solution temperature on adding NaCl to Phenol-Water system. Since NaCl is soluble only in water. If it has a lower consolute temperature, it is allowed by addition of third component. If the third component is soluble in both liquids roughly to the same extent, mutual solubility of liquid phase increases. The upper consolute temperature will be lowered or lower critical solution temperature will be raised. As a result, for e.g.: The addition of succinic acid or NaCl to phenol water system results in lowering of critical solution temperature.
PRINCIPLE: Addition of NaCl to phenol-Water system enhances its upper consolute temperature. The reasons are as follows:
NaCl is more soluble in water compared to its solubility in phenol in water layer. In the same way electrolyte present in the miscibility of aqueous layer in phenol layer. Therefore, temperature has to be increased to achieve mutual solubility. Therefore critical solution temperature of the system also increased. The increase in the critical solution temperature indirectly proportional to the concentration of NaCl. The linear relationship is used to determine the percentage composition of NaCl in water.
Applications:
- The addition of other ingredients to a conjugate solution may adversely effect their mutual solubility e.g.: Cresol with soap. According to B.P., 1968, contains 50% cresol. At this concentration, cresol is only partially miscible with water at room temperature. But the addition of soft soap to mixture makes cresol completely soluble in all proportions. This phenomenon is called as “SOLUBILISATION”. The principle is used in the preparation of phenolic disinfectant in water.
- The critical solution temperature method can be used to determine the percentage of composition of added substance using phenol-water system.
- It is possible to separate the liquids by the addition of third substance. The technique that is used here is applied for the extraction of drug in the analysis and body fluids.
GLASSWARE & CHEMICALS:
Transition temperature apparatus, Thermometer (110oC), beaker of 500ml, Volumetric flask of 100ml, pipette 10ml, gas burner, tripod stand, wire gauge, test tube, phenol, NaCl, weight box, fractional weight box.
PROCEDURE:
Stock solution Phenol (80%w/v):
Prepare 80%w/v of solution of phenol in water, by taking 20ml of water. At these proportions, water and phenol are completely miscible. This stock solution is used for the preparation of different concentration of phenol in water.
Stock solution, NaCl (1%w/v):
Accurately weigh 1gm of NaCl and transfer into a 100ml volumetric flask. Add distilled water and dissolve the salt. Finally make up the volume to 100ml.
METHOD :
- Prepare various concentration of NaCl ( 0.2%, 0.4%, 0.6%, 0.8%) in water (10ml) using the stock solution.
- Take 5ml of phenol and 5ml of water into the transition tube, dtermine the miscibility temperature T1.
- Remove transition tmperature tube from waterbath and stirr to allow cooling. Note the temperature at which opalascence reappears T2.
- Determine the mean of T1 & T2 and record in table. The data represents the “0” concentration of NaCl solution.
- Similarly, determine miscibility temperature of phenol-NaCl solution of various other concentrations of NaCl by following steps 3 & 4.
- Plot the graph of miscibility temperature ( Y-axis) various percentage concentration of NaCl ( X-axis).
- Determine miscibility temperature of unknown solution.
- Estimate the percentage composition of NaCl in the unknown soluiton from the standard plot drawn carrier.
Report:
- Critical solution temperature of unknown sample is __________ oC.
- The percentage composition of NaCl in the given sample ( from graph ) is _________ %.
Table:
Vol of phenol | %conc of NaCl | Miscibility temp | Turbidity temp | Avg temp
|
|
|
|
|
|
ESTIMATION OF pH BY USING pH METER
AIM : To measure the pH of a prepared buffer solution using pH meter.
PRINCIPLE :
An electric potential is generated when a thin glass membrane seperates two solutions of different hydrogen ion concentration. Then a solution is kept measuring pH, the difference in the potential between that of glass electrode and reference electrode is measured amplified and converted into a direct pH reading on the meter.
The pH meter measures the electromotive force (EMF) of concentrated cell formed from a reference electrodes, test solution and a glass electrode sensitive to hydrogen ion concentration. EMF og complete cell formed by linking of two electrodes i.e., glass electrode and calomel electrode is
E cell = E ref – E glass
Where E ref = potential of calomel electrode
E glass= potential of glass electrode, which depends on pH of the solution.
APPARATUS:
The pH meter consists of two electrodes
1. Calomel Electrode
2. Glass Electrode
The glass electrode contains silver, AgCl2 and 0.1N HCl. Its tip is covered by a special glass surface which allows only hydrogen ion to pass through it. Each of these component exists in an ionized state as follows
Inspite of above reactions there exists a complex and delicate equilibrium in glass electrode.
Calomel electrode contains mercury in contact with mercurous chloride which in turn is in contact with KCl solution at known concentration. The silver chloride electrode consists of silver wire coated with a deposit of KCl solution. In calomel electrode there is also a component that exist in delicate equilibrium
PROCEDURE:
MEASURING OF pH OF ACIDIC SOLUTION:
When the electrodes are placeod in acidic solution a concentration of H+ ion present on the outside of glass membrane increases, as a result the holes on the outer hydrated surface of glass electode are occupied by H+ ions produce due to break down of HCl combines with Cl- ions produce to give rise to the electrode potential, which is index of the pH of the solution.
MEASUREMENT OF pH OF BASE SOLUTION:
When the electrodes are placed in a basic solution which has concentration of OH- ions. The H+ ions from the outer hydrated layer if glass electrode leave their holes and combines with OH- ions of sample solution to give water molecule. Since the outside the holes become wettened more and protons from (HCl) solution inside the glass electrodes become bounded to inner membrane there by developing excessive negative charge. This difference in charge and two sides of glass electrodes results in electrode potential and as a result the pH of solution has measured.
MEASUREMENT OF pH OF NEUTRAL SOLUTION:
When an electrode is placed in a neutral solution, the H+ ions forms HCl present inside the glass electrodes become bound to the inner hydrated surface. This results in the release of equal number of protons from the holes of outer hydrated surface.
PRECAUTIONS:
v Before use of pH meter, it is needed to warm up atleast for 15min.
v pH meter is calibrated before use by meabs of a standard buffer solution. If there is any deviation in the pH meter is adjusted to correct standard value. The electrode should be washed with distilled water before and after use and must not be touched.
v The solution where pH has to measure should be stir well prior to its pH determination.
v The new electrode must be soaked in oil molal/litre HCl and distilled water is added for several hours before use.
v After use of electrode it should be kept in distilled water and are never allowed to dry up.
v Thus the pH of any given solution can be determined by pH meter.
REFERENCE BOOKS:
1. Practical Biochemistry by Srivastavi.
2. David T.Plummer of practical Biochemistry.
PREPARATION OF FLOCCULATED AND DEFLOCCULATED SUSPENSION
AIM: To prepare and evaluate flocculated and deflocculated suspensions..
PROCEDURE :
1. Weigh 5gm of Calcium carbonate and place in mortar add sufficient water and titrate until a smooth paste is obtained.
2. Dilute the paste with more of water until it is pourable and transfer the suspension in to a graduated measuring cylinder.
3. Rinse the mortar and pestle with sufficient number of times in order to transfer all the solids to the graduated measuring cylinder
4. Make the volume with water upto 100ml similarly prepare a suspension of calcium carbonate with a suspending agent like tragacanth.
5. By taking 0.5% of tragacanth aalong with calcium carbonate in first step.
6. Shake both the suspensions simultaneously to obtain uniform distribution and set aside without any disturbances.
7. Note the volume of the sediment with both suspensions at 0.5, 10,15,20,25,30,40,50 and 60 minutes.
8. Calculate sedimentation value and plot a graph taking sedimentation value against time.
REPORT:
S.No | Time in min | Volume of sediment without tragacanth | Volume of sediment with tragacanth | Sedimentation on volume without tragacanth | Sedimentate on volume with tragacanth. |
|
|
|
|
|
|
