Question detail
A sample of propane (C₃H₈) has a mass of 24.0 g. Calculate the number of moles of propane in the sample.
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At a glance
Question
Type
exam_style
Style
Topic
Carbon compounds as fuels and feedstock
Question
A sample of propane (C₃H₈) has a mass of 24.0 g. Calculate the number of moles of propane in the sample.
Answer
The sample contains 0.80 mol of propane. This is found by dividing the mass by the relative formula mass of propane (44.1 g mol⁻¹).
Explanation
The answer demonstrates the ability to apply the moles‑from‑mass relationship to a simple hydrocarbon, a key calculation skill for organic chemistry.
Common mistake
Mislabeling displayed formula as molecular formula
Students often write the same line‑bond diagram (displayed formula) and then state it as the molecular formula, forgetting that the molecular formula is a concise representation of the element counts, e.g. C₄H₁₀ for butane.
Explain that the displayed formula shows the connectivity of atoms, while the molecular formula lists the number of each element in the molecule. For butane, the displayed formula is CH₃–CH₂–CH₂–CH₃, the structural formula is the same with explicit bonds, and the molecular formula is C₄H₁₀.
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