Cambridge IGCSE Chemistry · Syllabus 0620 · Organic Chemistry
Alkane
What is Alkane?
A saturated hydrocarbon: a compound of carbon and hydrogen only in which every carbon-carbon and carbon-hydrogen bond is a single covalent bond, generally unreactive except in combustion and substitution by chlorine.
This definition is part of the Organic Chemistry chapter in Cambridge IGCSE Chemistry.
Common mistakes with Alkane
- 18. “C2H5OH + 3.5O2 → 2CO2 + 3H2O.” Core 11.6.2 defect The oxygen atom already inside the ethanol was not counted. why Alcohols differ from alkanes here: they bring one oxygen of their own to the left-hand side. repair Seven oxygen atoms are needed on the right; the ethanol supplies one, so O2 supplies six. The coefficient is 3. transfer Balance the complete combustion of ethanol again from a blank page, remembering its own oxygen, then check your coefficient against 3O2. Optional enrichment: methanol, CH3OH, behaves the same way — but only the combustion of ethanol is required by 0620, so do not learn another alcohol’s equation as though it were examinable.
- 19. “Alkanes are unreactive, so petrol does not really burn well.” Core 11.4.2 defect “Limited reactivity” read as “low vigour”. why The phrase restricts the number of types of reaction alkanes undergo, not how energetically those reactions proceed. repair Write: alkanes take part in few types of reaction — combustion, and substitution with chlorine under ultraviolet light — but combustion is vigorous and exothermic. transfer Explain why alkanes are still the basis of nearly every fuel in the fractionating column.