Extended Essays 2021

Hypothesis: If the duration of the synthesis of methyl salicylate ( 8 8 3 ) in the reflux system is increased, then the yield and percentage concentration of the synthesized methyl salicylate, determined

through the ferric chloride calibration curve and the UV spectrophotometer, would also increase

in the presence of sufficient reactants. This is because, as an esterification reaction undergoes

reflux for a longer duration, as outlined by the mechanism of the reaction, more water molecules

are be liberated from the alcohol-acid mixture due to the sufficient energy provided by the reflux

system. This therefore produces a higher concentration and yield of the desired ester, methyl salicylate, which is formed from the condensation reaction 14 .

Variables Independent Variable:

 Duration of reflux (1, 2, 3, 4 & 5 hours)

Increased by 1 hour for 5 variations

o

o Time controlled using the iPhone stopwatch/alarm

Dependent Variable:

 The light absorbance (Au) of synthesized methyl salicylate (in ferric chloride solution)

o Measured using the UV spectrophotometer (515nm) ( Appendix #1 )

o Measured 3 trials each for each of the reflux durations

 Mass (g) of synthesised Methyl salicylate solution

Measured using electronic balance

o

Controlled variables:

 Use of UV spectrophotometer to measure the absorbance value & electronic balance to

measure mass of synthesised methyl salicylate: controlled to ensure systematic limitations

associated with these equipment ( ±0.0001 for UV spec & ±0.0001 for electronic

balance) were equal throughout. The variation of equipment would result in varying

uncertainties and errors, directly affecting the accuracy of the data.

 Wavelength for the calibration of the UV spectrophotometer (515nm): Wavelength was

determined through scanning a ‘standard solution’ of methyl salicylate and ferric chloride to

find the peak wavelength, at which absorbs visible light ( Appendix #1 ).

 Concentration & volume of the reactants- Salicylic acid (28g/0.2 ), methanol (80 , 2.1mol) and conc. Sulfuric acid (8 , ~18mol): Concentrations were controlled

14 (Barnes, 2017)

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