SME
Grade 10 Science · Problem type
Alkenes: one double bond
Use this for an alkene’s formula and name: a chain with one carbon–carbon double bond, CₙH₂ₙ.
Diagram
1-butene, C₄H₈: every carbon makes 4 bonds and every hydrogen 1.
One double bond: hydrogens = 2 × 4 = 8.
This is an example. Type your own values to start a new problem.
C
H
Formulas
h
=
2
×
n
8 = 2 × 4
Assumptions
•
One carbon–carbon bond is double, here between the first two carbons (the 1- in 1-butene).
•
Alkene names end in -ene.
Step-by-step
WE KNOW
n = 4
FIND
hydrogen atoms (h)
Step 1 · Find hydrogen atoms (h)
Use h = 2 × n
Each carbon holds 2 hydrogens and the ends 2 more; the double bond takes 2 away.
h
=
2
×
4
4 carbons and one double bond: 1-butene, C₄H₈
h
=
8
Check
Put the numbers back in. Both sides should match.
8 = 2 × 4 ✓
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Organic chemistry: hydrocarbons, functional groups and polymers
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