Burning a candle is a combustion reaction that uses wax and oxygen to produce carbon dioxide, water, and energy. When you burn a candle down in an open room, the limiting reactant is .

In an open room, oxygen is continually available from the surrounding air, while the candle has only a limited amount of wax. The wax is used up first, so it is the limiting reactant. Energy is produced rather than consumed as a reactant, and water is a product of combustion.

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