This question is about alkanes - AQA - GCSE Chemistry - Question 1 - 2021 - Paper 2
Question 1
This question is about alkanes.
Table 1 shows information about some alkanes.
| Number of carbon atoms in alkane molecule | Boiling point of alkane in °C |
|------... show full transcript
Worked Solution & Example Answer:This question is about alkanes - AQA - GCSE Chemistry - Question 1 - 2021 - Paper 2
Step 1
Plot the data from Table 1 on Figure 2.
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
To plot the data, mark the following points on Figure 2:
(4, 0)
(5, 36)
(6, 69)
(7, 98) // estimated from the trend
(8, 126)
(9, 151)
Ensure accuracy by checking that points are correctly positioned based on the boiling points corresponding to the number of carbon atoms.
Step 2
Predict the boiling point X of the alkane with seven carbon atoms in a molecule.
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
X = 98 °C. Based on the trend from previous data and estimates, the boiling point for seven carbons is around 98 °C.
Step 3
Figure 2 is not suitable to show the boiling point of the alkane with three carbon atoms in a molecule. Suggest one reason why.
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 graph cannot show negative temperatures; the boiling point of the alkane with three carbon atoms is below 0 °C.
Step 4
Complete the formula of nonane.
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
C₉H₂₀.
Step 5
Explain why nonane will condense lower in a fractionating column during fractional distillation than the other alkanes in Table 1.
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
Nonane has a higher boiling point compared to the other alkanes listed. Therefore, it condenses where the column has a higher temperature, allowing it to remain as a gas longer within the column until an appropriate temperature is reached for condensation.
