Determination of boiling point

Determination of boiling point

1. Determination of
molecular weight By
Elevation Boiling Point
Prepared By:
Sara S. Sdiq
Zaynab Q. Salih
Raman R. Rasheed
Zaytun E. Ali
SalahaddinUniversity-Erbil
College Of science
Chemistry Department
2nd Stage
2022-2023
Supervised By:
Dr.RopakA.Sheakhmohamad
MS.Aveen.M Hanna

2. 1.Definition Of Boiling point
2.Colligative Properties of solution
3.Factors affecting Boiling point
4.Procedure
5.Calculation & definition of the symbols
Content

3. Definition
ØBoiling point
is the temperature at which the vaporpressure of the liquid is equal to
the atmospheric pressure andchange its state from a liquid to a gas.
ØIn terms of intermolecular interactions
the b.p. represents the energy required to overcome the various
intermolecular attractions binding the molecules as a liquid (e.g.
dipole-dipole attraction and hydrogen bonding). Therefore the
boiling point of a liquid is also an indicator of the strength of the
attractive forces between the liquid's molecules.

4. Colligative Properties
Of Solution
●Colligative properties are properties of
solutions that depend solely on the
number of particles dissolved in the
solution.
-The colligative properties do not depend
on the types of solute particles.
●Colligative properties are the physical
property Of Solution .

5. Colligative Properties Of
Solution
•There are four common types of
Colligative properties.
1. Vapor pressure lowering
2. Freezing point depression
3. Boiling point elevation
4. Osmotic pressure

6. Factors affecting
boiling point (b.p)
1.Pressure
2.Molecular weight
3.Impurities
4.Structure of the molecule &
intermolecular interactions
Like
A.Branching
B.Polarity
C.Van derwaalinteractions
D.H-bonding

7. Factors affecting boiling
point (b.p)
1.Pressure
a.When the pressure is less than 1 atm, the boiling point of the liquid is
less than its normal b.p.
b.When P = 1 atm, the b.p. of the liquid is called normal boiling
point
c.When P is greater than 1 atm, the b.p. of the liquid is greater than its
normal b.p.

8. Factors affecting
boiling point (b.p)
2. Molecular weight
By increasing molecular weight boiling point increase

9. Factors affecting boiling point
•The boiling point of pure H2O is 100 celsius, but that boiling point
can be elevated by adding a solute such as a salt.
3.Impurities
•A solution has higher boiling point pure solvent.

10. Factors affecting boiling point
4. Structure of the molecule & intermolecular interactions
A. Branching
Within the branched series, increased branch leads to lower boiling
point.

11. Factors affecting boiling point
4. Structure of the molecule & intermolecular interactions.
B. Polarity
Polarity rises boiling point.

12. Factors affecting boiling point
4. Structure of the molecule & intermolecular interactions
3. Van derwaalinteractions
As the number of carbon in an alkanes increase, the boiling point increase
due to the large surface area and van derwaalinteractions increased

13. Factors affecting boiling point
4. Structure of the molecule & intermolecular interactions
4. Hydrogen bonding
Hydrogen bonding increases the boiling point of a compound . This is
because hydrogen bonds are strong intermolecular attractive forces that
create stable molecules.

14. Procedure

15. Calculation
m=molal concentration of the solution we know thatmolality is the number of moles of solute per kilogram of the solvent
Now we know that molality is the number of moles of solute per kilogram of the solvent. Let the weight of solute be w2
having molar mass M2 dissolved in w1 grams of solvent. Then molality can be given as:
So , now, elevation boiling point is given by:
Now if we rearrange the above equation ,we get

16. Definition of the symbols
M2 = M.wt of the solute.g/mol
W2= weight of the solute.gm
W1=weight of the solvent. gm
m= molality of the solution. Mol/Kg
Kb = molal boiling point elevation constant, and it
is a constant characteristic of the solvent. Its unite is
(C°.kg/mol.).Kb depends only on nature of solvent and
not on the solute.

17. Reference
•Gelbspan, R., 2004. Boiling Point. Nation, 279(5), pp.24-26.
•Schmidt, H.J., Kaufmann, B. and Treagust, D.F., 2009. Students’ understanding of boiling
points and intermolecular forces. Chemistry Education Research and Practice, 10(4), pp.265-
272
•Pinarbasi, T., Sozbilir, M. and Canpolat, N., 2009. Prospective chemistry teachers’
misconceptions about colligative properties: boiling point elevation and freezing point
depression. Chemistry Education Research and Practice, 10(4), pp.273-280.
•Zaitseva, N., Dai, Z.R., Grant, C.D., Harper, J. and Saw, C., 2007. Germanium nanocrystals
synthesized in high-boiling-point organic solvents. Chemistry of Materials, 19(21), pp.5174-
5178.
Vancouver

18. Any Questions

19. Thanks