This question is about the preparation of hexan-2-ol - AQA - A-Level Chemistry - Question 5 - 2022 - Paper 2
Question 5
This question is about the preparation of hexan-2-ol.
Hexan-2-ol does not mix with water and has a boiling point of 140 °C.
Hexan-2-ol can be prepared from hex-1-en... show full transcript
Worked Solution & Example Answer:This question is about the preparation of hexan-2-ol - AQA - A-Level Chemistry - Question 5 - 2022 - Paper 2
Step 1
Suggest, with a reason, one other appropriate safety precaution for this experiment.
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Answer
Wear gloves to protect your hands from concentrated phosphoric acid, which is corrosive.
Step 2
Give a reason for adding the distilled water in steps c and f.
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The distilled water helps to remove any water-soluble impurities from the mixture.
Step 3
Give a reason for adding anhydrous magnesium sulfate in step h.
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Anhydrous magnesium sulfate is added to absorb any remaining water in the organic phase, ensuring a drier product.
Step 4
Complete and label the diagram of the apparatus used to filter the mixture under reduced pressure in step i.
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The diagram should include a vacuum flask connected to a vacuum pump, and a filter funnel on top. Label the funnel, flask, and the connection to the vacuum pump.
Step 5
Identify the most likely organic impurity, other than hex-1-ene, in the distillate collected in step j.
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Answer
The most likely organic impurity is hexan-3-ol.
Step 6
Suggest one reason why it could be difficult to remove this impurity.
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Hexan-3-ol is likely to have a similar boiling point to hexan-2-ol, making separation by distillation difficult.
Step 7
Calculate the mass, in g, of hexan-2-ol formed from 11.0 cm³ of hex-1-ene if the yield is 31.0%.
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Answer
First, calculate the mass of hex-1-ene:
extMass=extVolumeimesextDensity=11.0extcm3imes0.678extgcm−3=7.458extg
Using the molar ratio from the reaction, if we assume the molar mass of hexan-2-ol is approximately 102 g/mol, the theoretical yield would be calculated next. Then apply the yield percentage:
extActualmass=extTheoreticalmassimesextYield=7.458extgimes0.31=2.31extg
Rounding to one decimal place gives: 2.3 g.
