Chemical reactions of the alkenes
3 marks · Easy| Alkene | Number of Carbon Atoms | Number of Hydrogen Atoms | Can undergo addition reaction? (Yes/No) |
|---|---|---|---|
| Butene | 4 | 8 | Yes |
| Hexene | 6 | 12 | Yes |
| Nonene | 9 | 18 | Yes |
Based on the table, state the general relationship between the number of carbon and hydrogen atoms in these alkenes.
Explain why all three alkenes shown can undergo addition reactions.
Predict the number of hydrogen atoms in a molecule of pentene.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) The number of hydrogen atoms is double the number of carbon atoms · must show H = 2 × C
(b) They all have a carbon-carbon double bond · must show presence of C=C double bond
(c) 10 · must show correct calculation using CnH2n
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies relationship H = 2 × C, or the number of hydrogens is twice the number of carbons.
B1 (b) · 1 mark · States reason as having a carbon-carbon double bond (C=C).
A1 (c) · 1 mark · Correctly predicts 10 hydrogens in pentene.
Worked solution
a) The number of hydrogen atoms is double the number of carbon atoms (H = 2 × C).
b) All three have a C=C double bond, which allows addition reactions.
Therefore, pentene (C5) has 10 hydrogen atoms.