experimental measurement of boiling point elevation
TRANSCRIPT
Experimental Experimental measurement of boiling measurement of boiling
point elevationpoint elevation
Introduction And Some General Introduction And Some General TermsTerms
Boiling point.Non-volatile solutes.Non-electrolyte solutes.Dilute solutions & ideal solutions.Why addition of non-volatile solute.
increases boiling point.Boiling point elevation.Methods to find boiling point elevation.
What Is Boiling PointWhat Is Boiling Point
The temperature at which vapour pressure of a liquid becomes equal to its external pressure is called boiling point.
What Is Boiling PointWhat Is Boiling Point
As lower as the external pressure, less is the boiling point.
Non-volatile solutesNon-volatile solutes
The solutes which doesn’t evaporate at ordinary room temperature and have sufficient boiling point are called non-volatile solutes.
There may be either volatile or non-volatile solute they must form an ideal solution which is the main clause of colligative properties.
Non-electrolyte SoluteNon-electrolyte Solute
The solute which doesn’t dissociate when added in a solvent is called non-electrolyte solute.
Dissolving process in water
Na+
Cl-1. Overcome attractive forces in solid
2. Hydration of soluteOrientation of water molecules around solute
Click here for Chime structure
Ideal SolutionsIdeal Solutions
When the forces of attraction between the molecules of different components are same as when they were in the pure state the solutions are said to be ideal.
The volume of the solution must be equal to the individual volume of the components.
It should have zero enthalpy change as their heat of solution.
Dilute Solution Dilute Solution
The solution which has the low concentration of solute is called dilute solution.
It is one of the main conditions of boiling point elevation, that the solution must be dilute, ideal i.e. should have non-volatile and non-electrolytic components.
Why addition of non-volatile Why addition of non-volatile solute increases boiling point solute increases boiling point
The addition of a non-volatile solute increases the boiling point because
Non-volatile solute being bulky molecules bounce back the highly energetic molecule of the solvents.
This decreases the vapour pressure.Hence increases the boiling point.
PBPV
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Why addition of non-volatile Why addition of non-volatile solute increases boiling pointsolute increases boiling point
Why addition of non-volatile Why addition of non-volatile solute increases boiling pointsolute increases boiling point
Boiling Point ElevationBoiling Point Elevation
The increase in boiling point of a liquid when a non-volatile, non-electrolyte solute is added in it is called boiling point elevation.
Boiling Point ElevationBoiling Point Elevation
Methods To Determine Boiling Methods To Determine Boiling Point ElevationPoint Elevation
Elevation in boiling point can be determined, from which some methods are discussed here.◦Landsberger’s method.◦Cottrell’s method.◦Beckmann’s thermometer.
Landsberger’s MethodLandsberger’s Method
Apparatus.◦It consists of the following apparatus.
Boiling flask Delivery tube Graduated boiling tube Differential thermometer A hole to the middle of the boiling tube. Outer jacket Condenser
Landsberger’s MethodLandsberger’s Method
Landsberger’s MethodLandsberger’s Method
Working of apparatus.◦Boiling flask:-
In the boiling flask pure solvent is boiled.◦Delivery tube:-
The tube is used to transfer the vapours of pure solvent in landsburger’s method.
◦Graduated boiling tube:- It also contain small amount of pure solvent.
Landsberger’s MethodLandsberger’s Method
◦Differential thermometer:- It is the thermometer which reads change in
temperature not the temperature.◦Hole:-
This hole is in the middle of the boiling tube and is used to introduce a solvent in the boiling flask.
◦Outer jacket This is connected to an end with a condenser to
condense the outgoing vapours.
Landsberger’s MethodLandsberger’s Method
◦Condenser:- The condenser is used to condense the outgoing
vapours.
Landsberger’s MethodLandsberger’s Method
Procedure of landsberger’s method:-◦ Following this method is discribed step by
step.1. Taking pure solvent in boiling flask.2. Known volume in the boiling tube.3. Start heating to boil in the boiling flask.4. Vapours reach in the boiling tube.5. They boils the known volume of solvent
in the boiling tube.
Landsberger’s MethodLandsberger’s Method
Procedure of landsberger’s method:-6. Reading of the differential thermometer
is noted.7. This is the boiling point of pure solvent.8. Now a weighed amount of the solute is
introduced through HOLE.9. Vapours of pure solvent are continued to
pass through to boil the solution.
Landsberger’s MethodLandsberger’s Method
Procedure of landsberger’s method:-10. When solution boils temperature is
recorded for the boiling point of the solution.
11. Volume of the solution is noted at this stage.
12. Knowing the density of the solvent its mass can be calculated.
Landsberger’s MethodLandsberger’s Method
Procedure of landsberger’s method:-13. From the masses of solute and solvent
boiling point elevation can be calculated by the formula
∆Tb = 1000 w Kb/W m
Cottrell’s MethodCottrell’s Method
Cottrell’s method is superior than landsberger’s method as it over comes the errors of superheating occuring during landsburger’s method.
superheating:-◦ The heating of the vapours of a solvent
which increases its temperature from its boiling point is called superheating.
Cottrell’s MethodCottrell’s Method
Cottrell’s MethodCottrell’s Method
Apparatus:-◦It consists of the following apparatus.
Wide glass tube Sensitive differential thermometer Side tube Water Condenser Inverted funnel with bifurcated stem
Cottrell’s MethodCottrell’s Method
Working of apparatus:-◦Wide glass tube
It consists of pure solvent and thermometer is stuck in it
◦Differential thermometer It is used to read change in temperature
◦Side tube It is connected with condenser to convey the
vapours to the condenser
Cottrell’s MethodCottrell’s Method
Working of apparatus◦Water condenser
It condenses the vapours and return them to the tube
◦Inverted funnel The funnel has the vapours when the solvent is
heated which touches the thermometer.
Cottrell’s MethodCottrell’s Method
Procedure◦ The procedure is discribed step by step
1. Known amount of pure solvent is taken in the wide glass tube
2. Sensitive thermometer is placed at some distance from the solvent
3. The liquid is boiled and temperature is recorded
Cottrell’s MethodCottrell’s Method
4. Weighed amount of solute is introduced in the tube
5. Know solution is heated and the temperature is recorded which is the boiling point of the solution
6. In this experiment the vapours are condensed and then returned to the tube by water condenser.
Cottrell’s MethodCottrell’s Method
7. This time volume is noted and from density mass can be calculaed
8. From the masses of solute and solvent the elevation in boiling point can be calculated
9. This is the expression which is used to calculate the elevation
∆Tb = 1000 w Kb/W m
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