Unsaturated hydrocarbons
3 marks · Easy| Name | Number of carbon atoms | Number of hydrogen atoms |
|---|---|---|
| Ethene | 2 | 4 |
| Propene | 3 | 6 |
| Butene | 4 | 8 |
State the general formula for alkenes.
Complete the table for pentene.
Explain the pattern in the number of hydrogen atoms as the number of carbon atoms increases in alkenes.
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) CnH2n
(b) 5, 10 · must show 5 carbon atoms, 10 hydrogen atoms
(c) The number of hydrogens is always twice the number of carbons.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States the general formula for alkenes as CnH2n.
B1 (b) · 1 mark · Correctly fills in pentene row: 5 carbon atoms, 10 hydrogen atoms.
B1 (c) · 1 mark · Explains that the number of hydrogens is always twice the carbons in alkenes.
Worked solution
(a) The general formula for alkenes is CnH2n.
(b) For pentene, number of carbon atoms = 5, number of hydrogen atoms = 10.
(c) The number of hydrogens is always twice the number of carbons.