Vapor pressure and intermolecular forces

Introduction: 

In this experiment we are going to talk about vapor pressure and intermolecular forces. We are going to concentrate in butyl acetate (C₆H₁₂O₂) and we are going to show a molecule of this organic compound and the different parts the compound has. We also going to show a graph where we increase the temperature of butyl acetate to see how does the pressure change. At the end we can see a table of results with the boiling points, the temperature and the pressure of seven different compounds. 

Objectives in this lab session:

1.To improve practical skills – use of Schlenk tube, pressure sensors, vacuum line.

2.To investigate the structure and properties of one particular chemical.

3.To investigate the effect of temperature on vapour pressure.

4.To compare results with other groups (with other chemicals) and relate them to “intermolecular forces”.

Photos:

Butyl Acetate

Butyl Acetate is an organic compound commonly used as a solvent in the production of lacquers (cosmetic) and other products. It is a colorless flammable liquid. It is also found in many types of fruit, it gives a sweet smell of banana or apple. It is used as a synthetic fruit additive in foods such as candy, ice cream, cheeses, and baked goods.

Molecular formula: C₆H₁₂O₂

Molecular mass: 116.16 g mol^-1

Boiling point: 127 °C; 261 °F; 400 K

Graph:

Variation of pressure related to the time

Conclusion: More vapour is releases of the liquid when we increase the temperature so there are more molecules hitting the walls of the recipient so the pressure also increases.

Results:

Group	Chemical	Formula	Boiling point	Temperature and vapour pressure
1	Butyl Accetate	C6H12O2	20 ºC	0 ºC= 35,31 kPa // 15 ºC= 32,26 kPa // 20 ºC= 29,41 kPa // 40 ºC= 26,69 kPa
2	Diethyl Ether	(C2H5)2C	34,6 ºC	20 ºC= 38,2 kPa // 25 ºC= 44,3 kPa // 30 ºC= 64,5 kPa // 35 ºC= 102,2 kPa
3	Propyl Acetate	C5H10O2	102 ºC	0 ºC= 4,33 kPa // 15 ºC= 7,83 kPa // 20 ºC= 9,22 kPa // 40 ºC= 10,07 kPa
4	Ethyl Acetate	C4H8O2	77,1 ºC	0 ºC= 9,46 kPa // 15 ºC= 12,18 kPa // 21 ºC= 14,41 kPa // 40 ºC= 20,07 kPa
5	2-Propanol	C3H8O	82,5 ºC	0 ºC= 0,53 kPa // 15 ºC= 1,84 kPa // 20 ºC= 3,50 kPa // 40 ºC= 8,84 kPa
6	Pentate	C5H12	309,2 ºC	0 ºC= 71,42 kPa // 15 ºC= 98,63 kPa // 20 ºC= 101,93 kPa // 35 ºC= 104,94 kPa
7	Methyl Acetate	C3H6O2	56,9 ºC	0 ºC= 0,89 kPa // 15 ºC= 9,39 kPa // 20 ºC= 20,59 kPa // 35 ºC= 21,93 kPa

As we see in the table, the chemical with the highest boiling point is pentate with 309ºC, followed by propyl acetate with 102ºC and 2-propanol with 82.5ºC.

It has the highest boiling point because it has a large amount of Waals forces as it is a relatively large molecule. This makes the chemical have bigger instantaneous dipoles.

And we need more energy to separate the molecules. Pentane is the only molecule which only has Van der Waals forces so has the lowest boiling point.

COMPOUNDS: 

Butyl acetate:

diethyl ether:

Propyl acetate:

Ethyl acetate:

2-propanol:

Pentane:

Methyl acetate:

Bibliography: 

Recursostic.educacion.es.

Elementos y Compuestos

In-text: (Recursostic.educacion.es, 2014)

Bibliography: Recursostic.educacion.es. 2014. Elementos y Compuestos. [online] Available at: http://recursostic.educacion.es/secundaria/edad/3esofisicaquimica/3quincena7/3q7_index.htm [Accessed: 14 Mar 2014].

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