When most metallic elements are heated in the presence of oxygen, they undergo a

Question

When most metallic elements are heated in the presence of oxygen, they undergo a combustion reaction producing a metal oxide as the product. In an experiment of this type, a pure metal was heated in air then cooled and weighed. This process was repeated until the mass of the product was no longer changing. The data recorded in the notebook are shown below. What is the percent by weight of oxygen in the oxide product that was producedHeating a metal in air: initial mass of metal (g) = 1.74 mass after first heating (g) = 2.23 mass after second heating (g) = 2.49 mass after third heating (g) = 2.5

Explanation / Answer

Mass of metal before heating in oxygen = 1.74 g.

Work with the final mass of the metal oxide after heating (as the mass will no longer change when it has achieved a constant value). The mass of the metal oxide after heating = 2.5 g.

Mass of oxygen gained by the metal = (2.5 – 1.74) g = 0.76 g.

Percentage of oxygen in the oxide = (0.76 g)/(2.5 g)*100 = 30.4% (ans).

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