SME
Grade 10 Science · Problem type
Alkynes: one triple bond
Use this for an alkyne’s formula and name: a chain with one carbon–carbon triple bond, CₙH₂ₙ₋₂.
Diagram
Ethyne, C₂H₂: every carbon makes 4 bonds and every hydrogen 1.
One triple bond: hydrogens = 2 × 2 − 2 = 2.
This is an example. Type your own values to start a new problem.
C
H
Formulas
h
=
2
×
n
−
2
2 = 2 × 2 − 2
Assumptions
•
One carbon–carbon bond is triple, here between the first two carbons.
•
Alkyne names end in -yne: C₂H₂ is ethyne (acetylene).
Step-by-step
WE KNOW
n = 2
FIND
hydrogen atoms (h)
Step 1 · Find hydrogen atoms (h)
Use h = 2 × n − 2
Each carbon holds 2 hydrogens and the ends 2 more; the triple bond takes 4 away.
h
=
2
×
2
−
2
2 carbons and one triple bond: ethyne, C₂H₂
h
=
2
Check
Put the numbers back in. Both sides should match.
2 = 2 × 2 − 2 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
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Related lessons
Organic chemistry: hydrocarbons, functional groups and polymers
Main lesson
Alkenes: one double bond
Use this for an alkene’s formula and name: a chain with one carbon–carbon double bond, CₙH₂ₙ.
Isomers: a branched alkane
Use this for “Draw an isomer of pentane” or “How many hydrogens does 2-methylbutane have?”
Functional groups
Use this for “Which functional group does ethyl acetate have?”
Addition or condensation polymer?
Use this for “Is nylon an addition polymer or a condensation polymer?”