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20 ml methanol CH3OH 99.5%.
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20 ml ethanol C2H5OH 95.0%.
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20 ml propan-1-ol C3H7OH 98%.
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20 ml butan-1-ol C4H9OH 99%.
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20 ml octan-1-ol C8H17OH 94%.
- 3 x Pyrex test tubes.
- A Bunsen burner.
- A tripod.
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Metal thermometer (Uncertainty: ± 0.05 oC).
- 50 ml burette (Uncertainty: ± 0.500 ml).
- A funnel.
- A marker pen.
- 2 x Retort stands.
- 2 x clamps and bosses.
- The procedure uses poisonous and highly flammable alcohols. Notably, suggested by Department of Chemistry - Imperial College London (2006) , less than 2 teaspoons (2 ml) of methanol can cause blindness, and 2 table spoons (30 ml) can cause death. This toxicity is mainly due to it being converted in the body to formic acid and formaldehyde, which first attack the cells in the retina, then the other vital organs.
- Metal thermometer is used because glass thermometer is a potential source of cuts and lacerations and mercury thermometer has toxic mercury.
- Goggles and lab coat are therefore needed to be worn throughout the experiment.
- Close the tap and run some distilled water into the top of the burette, then swish the burette up and down to let the water clean all the inside of the burette. Open the tap, let the water drain out.
- Close the tap and use the funnel to put methanol into the burette.
- Put the test tube under the burette and open the tap to let 20 ml of methanol drain into the test tube, and use a marker pen to label methanol to distinguish among different alcohols.
- Use another retort stand with clamp and boss attached to clamp the test tube containing 20 ml of methanol.
- Place the tripod below the test tube.
- Use another clamp and boss to clamp the thermometer, make sure the bulb submerged in alcohol to measure and record the initial temperature.
- Place the Bunsen burner above heat resistant mat, right under the tripod.
- Immediately record the temperature when the alcohol boils.
- Wait for the test tube to cool down and then discard the remained alcohol.
- Repeat step 2 to step 9 twice with another test tube (same type) each time.
- Replace methanol by ethanol, propan-1-ol, butan-1-ol and octan-1-ol in step 1 respectively.
- Range and repetitions of experiment:
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There are 5 different ranges (The lowest value: 32.1 g mol-1 & the highest value: 130 g mol-1, Please refer to Data Collection and Processing -> Processed data).
- The whole experiment is repeated 3 times and 15 results are recorded.
- The volume of each alcohol remains constant for every test at 20 ml. Different volumes of the alcohol may cause inaccuracies in terms of comparing the time taken to boil. For instance, larger volume of the same liquid sample certainly takes longer time to be boiling.
- The thermometer will be clamped throughout the experiment and I will make sure the bulb submerged in alcohol, but not touching the bottom of the test tube to read the temperature carefully. This is because when the bulb touches the bottom of the test tube, the temperature read will be different.
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The same type of test tube will be used to prevent differences in surface area. This is due to the fact that larger surface area A (m2) will result higher heat input or output ΔQ (J) in the coefficient heat transfer, stated by Wikimedia Foundation:
where
ΔQ = heat input or heat lost, J
h = heat transfer coefficient, W/(m2K)
A = heat transfer surface area, m2
ΔT = difference in temperature between the solid surface and surrounding fluid area, K
Δt = time period, s.
- The burettes and funnels are rinsed carefully with distilled water prior to the experiment to ensure that inside the burettes do not contain any unnecessary substances/ions. If present, they may react with the alcohols to form products which affect the purity of alcohols.
