A student was carrying out an investigation into alcohols, aldehydes and ketones - Scottish Highers Chemistry - Question 6 - 2017
Question 6
A student was carrying out an investigation into alcohols, aldehydes and ketones.
(a) The student was given three alcohols labelled as A, B and C. These alcohols we... show full transcript
Worked Solution & Example Answer:A student was carrying out an investigation into alcohols, aldehydes and ketones - Scottish Highers Chemistry - Question 6 - 2017
Step 1
Draw a structural formula for the secondary alcohol with the formula C4H10O.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The structural formula for the secondary alcohol can be represented as:
H H OH
| |
H—C—C—C
| |
H H H
This shows that the hydroxyl (–OH) group is attached to the second carbon in the chain.
Step 2
Suggest why a water bath is an appropriate method of heating the reaction mixture.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
A water bath is an appropriate method for heating because it provides a controlled and even distribution of heat. This minimizes the risk of overheating and potential thermal decomposition of the reactants.
Step 3
Describe the colour change that would have been observed with alcohols A and C.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The colour change observed with alcohols A and C would be a change from orange to green. This indicates the reduction of the dichromate ion as the alcohol is oxidised.
Step 4
State the type of alcohol that cannot be oxidised by acidified dichromate solution.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Alcohol B is a tertiary alcohol, which cannot be oxidised by acidified dichromate solution.
Step 5
Complete the ion-electron equation for the oxidation reaction.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The ion-electron equation for the oxidation of alcohol A can be written as:
ightarrow C4H8O2 + 2H^+ + 2e^-$$
Step 6
Name the aldehyde that has a boiling point of 119 °C.
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The aldehyde that has a boiling point of 119 °C is 2-methylpentanal.
Step 7
Predict the boiling point, in °C, of the following molecule.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The predicted boiling point of the molecule H3C-CH2-CH2-CHO would be around 166 °C. This is based on its size and molecular interactions compared to the aldehydes listed.
Step 8
Describe one way in which differences in structure affect the boiling point of isomeric aldehydes.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
One way differences in structure affect boiling points is through branching. More branching in isomeric aldehydes typically lowers the boiling point due to reduced surface area, leading to weaker van der Waals forces.
Step 9
State what would be observed when an aldehyde is gently heated with Tollens’ reagent.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
When an aldehyde is gently heated with Tollens’ reagent, a silver mirror or silver precipitate would be observed, indicating the reduction of silver ions.
Step 10
Name the type of intermolecular interaction between ketone molecules.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The type of intermolecular interaction between ketone molecules is permanent dipole to permanent dipole interaction.
Join the Scottish Highers students using SimpleStudy...
