1. MEGHA SAXENA Bsc.(H) CHEMISTRY 2 nd year Roll.No.-00-131 ByBy

3. AIM DETERMINE THE ELEVATION IN BOILING POINT OF WATER WHEN LACTOSE IS ADDED TO IT

4. APPARATUS REQUIRED Kjeldhals flask Thermometer Cork Capillary Ignition tube Thread Clamp-stand Sand-bath Burner Electrical balance Test -tube

5. CHEMICALS REQUIRED Concentrated sulfuric acid Lactose Distiled water

6. THEORY Purpose of doing this experiment. I choose this experiment because I want to know that it happens with all solutes or not. I choose lactose as solute not other. This is because on addition of sugar boiling point of water increases and sugar is a part of glucose which further is a part of lactose. So I choose lactose because as on addition of sugar boiling point increases,so same is happen in case of lactose or not.

7. Elevation in boiling point. D efinition of boiling point: a liquid starts boiling when its vapour pressure becomes equal to the external pressure.this temperature is known as boiling point of the liquid. When a nonvolatile solute is added to a liquid solvent,the boiling point of the resultant solution is increased. Definition of elevation in boiling poin t The vapour pressure of the solution is comparatively smaller than that of pure solvent(raoult s law). Consequently, the temperature at which the vapour pressure of solution becomes equal to the external pressure, will be greater than that of pure solvent,thus raising its boiling point.

8. FORMULAE USED ∆ T b =K b m Here ∆T b =T b -T b *,the elevation in boiling point. K b =(M 1 RT b *2)/∆vap Hm. it is boiling point elevation constant. its unit is K kg /mol. m is the molality of the solution. m=(W 2 x1000)/(M 1 xW 1 ) Van t hoff equation =(observed colligative property)/(calculated colligative property) i=(∆T b ) obs /(∆T b ) cal

9. PROCEDURE DETERMINATION OF BOILING POINT OF WATER Clean all apparatus with water and rinse with distilled water. Fill the kjeldhals flask 1\4 th by concentrated sulfuric acid. Take a capillary and close its one end by rotating it in flame. Take an ignition tube and put a drop of distilled water in it. Put capillary in it inverted(in such a way that its open end is dipped in water and closed end,

10. Outside the ignition tube. Place this thermometer in kjeldhals flask in such a way that the tip of thermometer should dip in sulfuric acid. Heat the kjeldhals flask till first bubble appears. When bubbles come continuously note the temperature. Remove the burner and wait when bubbles stop coming and liquid rise in capillary. Note the temperature again. This is the boiling point of the water.

11. DETERMINATION OF BOILING POINT WHEN LACTOSE IS ADDED Weigh 0.01g of lactose. Dissolve it in 5g distilled water. Put a drop of it in ignition tube and bind ignition tube with a thermometer Put a capillary in it inverted whose open side should be inside the liquid. Place the thermometer in kjeldhals flask and heat the flask. Till continuous bubbling start. Note the temperature when liquid rise in capillary. This is the boiling point of liquid. Repeat the process on every addition up to 0.05. Find the elevation at every addition.

12. CALCULATION FOR PREPARATION p reparation of 0.1 molar solution of lactose. let the mass of lactose is X 0.1=(X x 1000)/(360.31 x 5) X=(0.1 X 360.31 X5)/1000 X=0.18 Similarly,

13. OBSERVATIONS

14. CALCULATION

15. RESULT Since van t hoff factor is not same.hence this shows that lactose do not show colligative properties, and as elevation in boiling point is a colligative property so we cannot find the elevation in boiling point of lactose.

16. CONCLUSION Elevation in boiling point is; When a small amount of solute is added in the solvent,it increases its boiling point,this is known as elevation in boiling point. Here lactose is taken as solute and distilled water as solvent. The boiling point of pure water is 100 degree Celsius When lactose added the boiling point should increase. But when the solution of lactose and water heated it starts boiling at 104 degree but the boiling point is not constant. It increases for a moment then decreases again i.

17. It does not give a sharp boiling point. This happens due to the following reason Lactose on hydrolysis converts into its monosaccharide components, glucose and galactose. This is because lactose is a reducing sugar. so it exibit muta-rotation. and is 1,4-beta- glycoside. These two forms are known as α and β.

18. STRUCTURE OF LACTOSE THIS IS THE STRUCTURE OF LACTOSE. THIS IS 1,4-BETA-GLYCOSIDE

19. CONCLUSION Lactose has two type of anomers α and β. The α and β forms are differ in their physical properties. A molecule of water is associated with crystalline α form of lactose and so it is referred as mono hydrated At temperature over 120ׂ۫c and under vacuum,however this water is lost and highly hygroscopic α-lactose anhydrous is formed. When lactose is dissolved in water mutarotation occurs,i.e; α and β anomers inter converts

20. CH2OH O OH CH2OH OOH O H2O OO CH2OH OH CH2OH OH O INTERCONVERSION Of α-FORM INTO β -FORM galactos e glucos e

21. INTERPRETATION Since two forms are inter convertible above100 degree Celsius. Thats why above 100 degree Celsius it shows variation. Hence colligative property of lactose cannot be studied