SME
Grade 10 Science · Chemistry
Organic chemistry: hydrocarbons, functional groups and polymers
Use this for “Name the alkane with 3 carbons and write its formula,” with CₙH₂ₙ₊₂.
Diagram
Propane, C₃H₈: every carbon makes 4 bonds and every hydrogen 1.
Hydrogens = 2 × 3 + 2 = 8.
This is an example. Type your own values to start a new problem.
C
H
Formulas
h
=
2
×
n
+
2
8 = 2 × 3 + 2
Assumptions
•
Carbon makes four bonds, hydrogen one.
•
Alkanes have only single bonds: CₙH₂ₙ₊₂.
•
The prefix counts carbons: meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-.
Step-by-step
WE KNOW
n = 3
FIND
hydrogen atoms (h)
Step 1 · Find hydrogen atoms (h)
Use h = 2 × n + 2
Each carbon holds 2 hydrogens, plus 1 more at each end of the chain (methane: 2 + 2).
h
=
2
×
3
+
2
3 carbons and only single bonds: propane, C₃H₈
h
=
8
Check
Put the numbers back in. Both sides should match.
8 = 2 × 3 + 2 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
Refresh
More problem types
Alkenes: one double bond
Use this for an alkene’s formula and name: a chain with one carbon–carbon double bond, CₙH₂ₙ.
Alkynes: one triple bond
Use this for an alkyne’s formula and name: a chain with one carbon–carbon triple bond, CₙH₂ₙ₋₂.
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?”