Existence of Hydrogen Bonds Between Ethanol Molecules

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Experiment 9

Aim

A. To investigate the existence of hydrogen bonds between ethanol molecules. B. To measure the strength of hydrogen bond formed between ethanol molecules C. To investigate the formation of hydrogen bonds between molecules of ethyl ethanoate and trichloromethane. D. To measure the strength of hydrogen bond formed between molecules of ethyl ethanoate and trichloromethane.

Procedure

A.

1. 10 cm3 of ethanol was added into an insulated 50 cm3 beaker by using a measuring cylinder. The temperature of the liquid was measured. 2. 10 cm3 of cyclohexane was added to the ethanol in the beaker. It was then mixed well and the lowest temperature attained was recorded.

B.

1. 10 cm3 of ethanol was added into an insulated 50 cm3 beaker by using a measuring cylinder. The temperature of the liquid was measured. 2. 20 cm3 of cyclohexane was added to the ethanol in the beaker. It was then mixed well and the lowest temperature attained was recorded.

C.

1. 10 cm3 of ethyl ethanoate was measured into an insulated beaker. Its temperature was recorded. 2. This was added to 10 cm3 of trichloromethane and was mixed well. The highest temperature attained was recorded.

D.

1. 10 cm3 of ethyl ethanoate was measured into an insulated beaker. Its temperature was recorded. 2. This was added to 10 cm3 of trichloromethane and was mixed well. The highest temperature attained was recorded.

Result

Temperature change of solution

| |A |B |C |D | |Initial(oC) |19.5 |20.5 |20 |18 | |Final(oC) |16 |16.5 |27 |26 | |Net(oC) |-3.5 |-4 |7 |8 |

Calculation

|Liquid |Formula |Relative Molecular|Density |Specific heat capacity | | | |mass |/kg dm3 |/kJ kg-1 K-1 | |Ethanol |CH3CH2OH |46 |0.81 |2.44 | |Cyclohexane |C6H12 |84 |0.78 |1.83 | |Trichloromethane |CHCl3 |119.5 |1.48 |0.98 | |Ethyl ethanoate |CH3CO2CH2CH3 |88 |0.9 |1.92 |

B.

Mass of Ethanol: 0.81((10(10-6)=0.0000081kg

Mass of Cyclohexane: 0.78((20(10-6)=0.0000156kg

Total heat absorbed:

4((0.0000081(2.44+0.0000156(1.83)

=0.000193248 kJ

mole of limiting reactant (i.e. ethanol):

0.0000081(1000/46=0.000176086 mole

The enthalpy change for one mole of ethanol that the hydrogen bond was broken is:

0.000193248/0.000176086

=1.09746 kJ/mole

D.

Mass of ethyl ethanoate: 0.9((20(10-6)=0.000018kg

Mass of trichloromethane: 1.48((10(10-6)=0.0000148kg

Total heat absorbed:

8((0.000018(1.92+0.0000148(0.98)

=-0.000392512kJ

mole of limiting reactant (i.e. trichloromethane):

0.0000148(1000/119.5

=0.000123849mol.

The enthalpy change for one mole of trichloromethane that formed hydrogen bond is:

-0.000392512/0.000123849=-3.1693 kJ per mole

Conclusion

A. The mixing process between ethanol and cyclohexane is endothermic. B. The enthalpy change for one mole of ethanol with hydrogen bond broken after mixed with Cyclohexane is 1.09746 kJ/mole. C....
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