MediumChemistryHigh School (9–10)GeneralCarbon and Its Compounds › Reactions and Uses of Carbon CompoundsNumericalBoard Exam
Find the percentage of carbon, by mass, in propyne, C₃H₄, and in propane, C₃H₈…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Find the percentage of carbon, by mass, in propyne, , and in propane, . Which one burns with a sootier flame in air, and why? (, .)
Need a reminder? The key ideaShow
Combustion gives carbon dioxide, water, heat and light. Saturated fuels burn with a blue flame; unsaturated ones, or too little air, give a yellow, sooty flame. Oxidising agents turn alcohols into acids. Unsaturated compounds add hydrogen with a nickel catalyst. Saturated ones swap a hydrogen for chlorine in sunlight.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Propyne. carbon.
Step 2. Propane. carbon.
Step 3. The flame. Propyne has more carbon in each gram. The air cannot burn it all, so some is left as soot.
Answer: propyne and propane ; propyne is sootier.
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