2yr.chem,1yr.chem projects

Rate of Evaporation of Different Liquids

 Objective of the Project

This project is of the rate of evaporation of different liquid, in which we also discuss the factors which affect the rate of liquid.

 Introduction

When liquid is placed in an open vessel. It slowly escapes into gaseous phase ventually leaving the vessel empty. This phenomenon is known as vaporization or evaporation. Evaporation of liquids can be explained in the terms of kinetic molecular model although there are strong molecular attractive forces which hold molecules together. The molecules having sufficient kinetic energy can escape into gaseous phase. If such molecules happen to come near the surface in a sample of liquid all the molecules do not have same kinetic energy. There is a small fraction of molecules which have enough kinetic energy to overcome the attractive forces and escapes into gaseous phase.

Evaporation causes cooling. This is due to the reason that the molecules which undergo evaporation have high kinetic energy therefore the kinetic energy of the molecules which are left behind is less.

Since the remaining molecules which are left have lower average kinetic energy. Therefore temperature is kept constant the remaining liquid will have same distribution of the molecular kinetic energy and high molecular energy will kept one escaping from liquid into gaseous phase of the liquid is taken in an open vessel evaporation will continue until whole of the liquid evaporates.

Factors affecting the rate of evaporation

(1) Nature of Liquids : The magnitude of inter-molecular forces of attraction in liquid determine the speed of evaporation. Weaker the inter-molecular forces of attraction larger is the extent of evaporation. In diethyl ether rate of evaporation is greater than that of ethyl alcohol.

(2) Temperature : The rate of evaporation of liquids varies directly with temperature. With the increase in the temperature, fraction of molecules having sufficient kinetic energy to escape out from the surface also increases. Thus with the increase in temperature rate of evaporation also increases.

(3) Surface Area : Molecules that escape the surface of the liquids constitute the evaporation. Therefore larger surface area contributes accelerating evaporation.

(4) Composition of Environment : The rate of evaporation of liquids depends upon the flow of air currents above the surface of the liquid. Air current flowing over the surface of the liquid took away the molecules of the substance in vapour state there by preventing condensation.

Experiment no. 1

Aim : To compare the rates of evaporation of acetone, benzene and chloroform.

Requirement : Three same size Petri dishes of diameter 10 cm., 10 ml. pipettes, stop watch, acetone benzene and chloroform.

Procedure :

1. Clean and dry all Petri dishes and identify them as A, B and C.

2. Pipette out of 10 ml. acetone in Petri dish "A" with stopper similarly pipette out of 10 ml. of benzene and chloroform in each of Petri "B" and "C".

3. Remove the cover plates from all Petri dishes and start the stop watch.

4. Let the Petri dishes remain exposed for 10 minute. Now cover each of the petri dish and note the volume of remaining material in them.

Observation :

Time : 10 min. = 600 Sec.

Petri dishes Marked	Liquid Taken (V1) ml.	Volume remaining (V2) ml.	Vol. Evap. V=V1–V2	Rate (V/T) ml./s
A	10	2	8	8/600=0.0133
B	10	3	7	7/600=0.0116
C	10	4	6	6/600=0.010

 Results :

Rate of evaporation of Acetone is 0.0133 ml/s.

Rate of evaporation of Benzene is 0.0166 ml/s.

Rate of evaporation of Chloroform is 0.010 ml/s.

Conclusion :

The intermolecular forces of acetone, benzene and chloroform are in order.

Chloroform > Benzene > Acetone.

Experiment no. 2

Aim : To study the effect of surface area on the rate of evaporation of diethylether.

Requirement : Three Petri dishes of diameter 2.5 cm., 5 cm., 7.5 cm. with cover, 10 ml. of pipette and stop watch.

Procedure :

1. Clean and dry all Petri dishes and mark them as A, B and C.

2. Pipette out of 10 ml. diethylether in each of the Petri dishes A, B and C and cover them immediately.

3. Uncover all three Petri dishes and start the stop watch.

4. Note the remaining volume after 10 min. vaporization of diethyl ether from each Petri dish.

Observation :

Time : 10 min. = 600 Sec.

Petri dishes Marked	Diameter of P.T.Ds.	Volume Taken (ml.)	Remaining Vol. (ml.)	Evaporated volume
A	2.5	10	4	6
B	5.0	10	2	8
C	7.5	10	0	10

Results : The order of evaporation of acetone in three petri dishes as 7.5 > 5.0 > 2.5 cm.

Conclusion : Larger the surface area more is evaporation.

Experiment no. 3

Aim : To study the effect of temperature on the rate of evaporation of acetone.

Requirement : Two Petri dishes of 5 cm. diameter each stop watch, 10 ml. pipette, thermometer, thermostat.

Procedure :

1. Wash and Clean, dry the Petri dishes and mark them as A, B.

2. Pipette out of 10 ml. of acetone to each of Petri dishes A and B and cover them.

3. Put one Petri dish at room temperature and to the other heat for same time.

4. Note the reading.

Observation :

Time : 10 min. = 600 Sec.

Petri dishes Marked	Time (Sec.)	Temperature (0C)	Volume Taken (ml.)	Evaporated volume (ml.)
A	10	30	10	10
B	20	40	10	10

Results : The order of evaporation of acetone in two Petri dishes as given

Room Temperature < Heating.

Conclusion : Observation clearly shows that the evaporation increases with temperature.

Experiment no. 4

Aim : To study the effect of air current on the rate of evaporation of acetone.

Requirement : Two Petri dishes acetone.

Procedure :

1. Clean and dry the Petri dishes and mark them as A and B.

2. Keep one dish where no air current and other under a fast air current.

3. Note the reading.

 Observation :

Initial Volume 10 ml. of Acetone.

Petri dishes Marked	Conditions	Time (Sec.)	volume Evaporated (ml.)
A	With fan	40	10
B	without fan	50	10

Results : The order of evaporation of acetone in two Petri dishes as given

With fan > Without Fan..

Conclusion : The rate of evaporation of liquid increases with the increase in rate of flow of air current.

 2

AIM

To study the presence of oxalate ions in guava fruit at different stages of ripening.

 Introduction

Guava is a common sweet fruit found in India and many other places around the world.

Guavas

Are plants in the Myrtle family (My tracheae) genus Psidium (meaning "pomegranate" in Latin), which contains about 100 species of tropical shrub. On ripening it turns yellow in color. Rich in vitamin C, this fruit is a rich source of oxalate ions whose content varies during the different stages of ripening. Guavas have a pronounced and typical fragrance, similar to lemon rind but less in strength.t is a carboxylic acid, primarily found in plants and animals. It is not an essential molecule and is excreted from our body, unchanged. Our body either produces oxalate on its own or converts other molecules like Vitamin C to oxalate. External sources like food also contribute to the accumulation of oxalate in our body. The oxalate present in the body is excreted in the form of urine as waste. Too much of oxalate in our urine results in amedical condition called hyper oxaluria, common lyreferred to as kidney stones. Diet is looked upon as a preventive    measure in addition to medication to retreat kidney stones. 

Theory

Oxalate ions are extracted from the fruit by boiling pulp with dilute H2SO4.

The oxalate ions are estimated volumetrically, by titrating the solution with KMnO4

solution. A reagent, called the titrant, of a known concentration (a standard solution) and volume is used to react with a solution of the analyte or titrand, who second centration is not known. Using a calibrated burette or chemistry pipetting syringe to add the titrant, it is possible to determine the exact amount that has been consumed when the endpoint is reached. The endpoint is the point at which the titration iscomplete, as determined by an indicator. This is ideally the same volume as the equivalence point. He volume of added titrant at which the number of moles of titrant is equal to the number of moles of analyte, or some multiple thereof (asin polyprotic acids). In the classic strong acid-strong base titration, the endpoint of a titration is the point at which the pH of the reactant is just about equal to7, and often when the solution takes on a persisting solid colour as in the pink of phenolphthalein indicator.

 

 (A) Apparatus

100 ml measuring flask Pestle & Mortar Beaker Burette Funnel Weighing machine Filter Papers

 (B) Chemicals

1.dil. H2SO4

 2.(N/10)KMnO4  solution

(C)  Guava fruits at different stages of ripening.

 

Procedure

(1) Weighed 50 g of fresh guava and crushed it to a fine pulp using pestleand mortar.

(2) Transferred the crushed pulp to a beaker and added about 50 ml dilute H2SO4  to it.

(3) Boiled the content for about 10 minutes. Cooled and filtered the contents in a 100 ml measuring flask.

(4) Made up the volume 100 ml by adding ample amount of distilled water.

(5) Took 20 ml of the solution from the flask and added 20 ml of dilute sulphuric acid to it.

(6) Heated the mixture to about 60⁰C and titrated it against (n/10) KMnO4

      solution taken in a burette till the end point had an appearance of pink colour.

(7) Repeated the above experiment with 50 g of 1day, 2 day and 3 day old guava fruits.

Precautions

There should be no parallax while taking measurements.  

Spillage of chemicals should be checked.

Avoid the use of burette having a rubber tap as KMnO4 attacks rubber. In order to get some idea about the temperature of the solution touch the flask with the back side of your hand.

When it become sun bearable to touch, the required temperature is reached.

Add about an equal volume of dil. H2SO4 to the guava extract to be titrated (say a full test tube) before adding KMnO4 .

Read the upper meniscus while taking burette reading with KMnO4solution.

In case, on addition of KMnO4  a brown ppt. appears, this shows that either H2SO4 has not been added or has been added in insufficient amount. In such a case, throw away the solution and titrate again.

Observations

 1. Weight of the guava fruit for each time was 50 g.

 2. Volume of guava extract taken for each titration was  20 ml.

 3. Normality of KMnO4 solution was (1/10).

4. END POINT:  Colour Changes to pink

Guava Solution	Burette reading Initial	Final Reading	Volume of KMnO4	Concurrent Reading
Raw	150	18	132	136.06
semi-ripened	150	13	137
Ripened	150	10.8	139.2

The content of oxalate ions in guava was found to be 59.67 per cent, which is close to the literature value of 60 percent. It was also noticed that the content of oxalic ions grows with ripening of guava.

Calculations

1) For raw guava

    N1V1 = N2V2

 N1 x 10 = (1/10) x132

 1/10 x Normality of oxalate = (x/100) = strength of oxalate in freshguava extract = normality x Eq. mass of oxalate ion= 1.32/100 x 44g/litre of diluted extract= 0.581 g L-1

 2) For semi ripened guava (1 day old).Strength of oxalate in one day old guava extract= (1.37 /100) x 44g/ litre of  

     diluted extract= 0.603 g L-1

 3) For ripened guava Strength of oxalate in fresh guava extract= ( 1.39/100) x 44g/ litre of diluted extract=0.612g

     L-1

RESULTS

(a) The normality of oxalate ions of;

(i)  Fresh guava solution is = 1.32 ml

(ii) Semi-ripen guava solution is = 1.37 ml

(iii) Ripened guava solution is = 1.39 ml

(b) The strength of oxalate ions of;

(i)  Fresh guava solution is = 0.58 ml

(ii) Semi-ripened guava is = 0.60 ml

(iii) Ripened guava is = 0.61 ml

Conclusions

The content of oxalate ions in guava was found to be 59.67 per cent, which is close to the literature value of 60 percent. It was also noticed that the content of oxalic ions grows with ripening of guava.

 

4. END POINT:  Colour Changes to pink

Guava Solution	Burette reading Initial	Final Reading	Volume of KMnO4	Concurrent Reading
Raw	150	18	132	136.06
semi-ripened	150	13	137
Ripened	150	10.8	139.2

The content of oxalate ions in guava was found to be 59.67 per cent, which is close to the literature value of 60 percent. It was also noticed that the content of oxalic ions grows with ripening of guava.

Calculations

1) For raw guava

    N1V1 = N2V2

 N1 x 10 = (1/10) x132

 1/10 x Normality of oxalate = (x/100) = strength of oxalate in freshguava extract = normality x Eq. mass of oxalate ion= 1.32/100 x 44g/litre of diluted extract= 0.581 g L-1

 2) For semi ripened guava (1 day old).Strength of oxalate in one day old guava extract= (1.37 /100) x 44g/ litre of  

     diluted extract= 0.603 g L-1

 3) For ripened guava Strength of oxalate in fresh guava extract= ( 1.39/100) x 44g/ litre of diluted extract=0.612g

     L-1

RESULTS

(a) The normality of oxalate ions of;

(i)  Fresh guava solution is = 1.32 ml

(ii) Semi-ripen guava solution is = 1.37 ml

(iii) Ripened guava solution is = 1.39 ml

(b) The strength of oxalate ions of;

(i)  Fresh guava solution is = 0.58 ml

(ii) Semi-ripened guava is = 0.60 ml

(iii) Ripened guava is = 0.61 ml

Conclusions

The content of oxalate ions in guava was found to be 59.67 per cent, which is close to the literature value of 60 percent. It was also noticed that the content of oxalic ions grows with ripening of guava.