Alkanes
3 marks · EasyThis question is about the unbranched alkane with seven carbon atoms.
Write the name of this alkane.
Give its molecular formula.
Draw its displayed (structural) formula.
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) heptane · must show heptane
(b) C7H16 · must show C7H16
(c) — · must show 7 carbon atoms in a single straight chain, each with correct number of hydrogens (ends: 3, middle: 2), all bonds shown
Must show: heptane, C7H16, seven carbons in a straight chain with correct number of hydrogens
Common mistakes: Wrong chain length or name, missing hydrogens
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct name: heptane.
B1 (b) · 1 mark · Correct molecular formula: C7H16.
B1 (c) · 1 mark · Displayed formula is correct: seven C in a straight line, each carbon showing correct number of hydrogens.
Worked solution
a) The alkane with seven carbon atoms is called heptane.
b) Its molecular formula is .
c) Displayed formula:
CH3—CH2—CH2—CH2—CH2—CH2—CH3 (all bonds between carbons and all hydrogens should be drawn out).