ExpertEasy1 markMultiple Choice
AQA GCSE · Question 02.2 · Organic chemistry
What type of carbon compound is octane, C₈H₁₈?
What type of carbon compound is octane, C₈H₁₈?
Answer options:
A.
Alcohol
B.
Alkane
C.
Carboxylic acid
D.
Ester
How to approach this question
Look at the chemical formula for octane: C₈H₁₈. Identify the elements present. Recall the general formula for alkanes, CₙH₂ₙ₊₂. Check if octane's formula fits this general formula.
Full Answer
B.Alkane✓ Correct
Alkane
Octane (C₈H₁₈) is a hydrocarbon because it contains only hydrogen and carbon atoms. To determine if it is an alkane, we check the general formula for alkanes: CₙH₂ₙ₊₂.
Let n = 8 (the number of carbon atoms).
The number of hydrogen atoms should be 2n + 2 = (2 × 8) + 2 = 16 + 2 = 18.
The formula C₈H₁₈ matches the general formula for alkanes, so octane is an alkane.
Common mistakes
✗ Confusing alkanes with other homologous series like alkenes (CₙH₂ₙ).
✗ Selecting a compound type that contains oxygen (alcohol, carboxylic acid, ester) when the formula only shows carbon and hydrogen.
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