Modern shellac nail varnishes are more durable and so last longer than traditional nail polish - Scottish Highers Chemistry - Question 7 - 2016
Question 7
Modern shellac nail varnishes are more durable and so last longer than traditional nail polish.
(a) The Skin Care Foundation has recommended that a sun-block is app... show full transcript
Worked Solution & Example Answer:Modern shellac nail varnishes are more durable and so last longer than traditional nail polish - Scottish Highers Chemistry - Question 7 - 2016
Step 1
Suggest why the Skin Care Foundation makes this recommendation.
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Answer
The Skin Care Foundation recommends applying sun-block to protect the skin from UV radiation. UV light can cause skin damage, leading to sunburn and even increasing the risk of skin cancer. Additionally, UV light can initiate free radical reactions damaging the skin and promoting premature aging.
Step 2
State what is meant by the term free radical.
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A free radical is a species that has one or more unpaired electrons, making it highly reactive and able to participate in chemical reactions.
Step 3
State the term used to describe this type of step in a free radical chain reaction.
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The type of step described is known as initiation, where radicals are generated to start the chain reaction.
Step 4
Name the functional group circled above.
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The functional group circled above is a carboxylic acid group.
Step 5
State why propan-2-ol can be described as a secondary alcohol.
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Propan-2-ol is classified as a secondary alcohol because the hydroxyl group (-OH) is attached to a carbon atom that is bonded to two other carbon atoms.
Step 6
Draw a structural formula for butyl ethanoate.
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The structural formula for butyl ethanoate is:
H H H
| | |
H - C - C - C - C - O - C = O
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H H H
or alternatively:
H H
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H - C - C - O - C = O
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H H
H
Step 7
Suggest why a wet paper towel is wrapped around the test tube.
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Answer
A wet paper towel is wrapped around the test tube to condense any vapors or reactants that may evaporate during the reaction. This helps to manage temperature and keep the reactants in liquid form.
Step 8
Calculate the percentage yield of ethyl ethanoate.
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To calculate the percentage yield of ethyl ethanoate:
Calculate the theoretical mass of ethyl ethanoate produced:
Molar mass of ethanol = 46 g/mol
Molar mass of ethanoic acid = 60 g/mol
Molar mass of ethyl ethanoate = 88 g/mol
The reactants used were 2.5 g of ethanol (0.054 moles) and an excess of ethanoic acid.
Actual yield = 2.9 g.
Percentage yield = (Actual yield / Theoretical yield) * 100. Assuming theoretical yield is obtained using stoichiometry:
