Although a compound is a pure substance, it contains two or more elements combined chemically. Select each of the following that is an example of a mixture of pure elements and does not include one or more chemical compounds. iron (III) oxide (Fe2O3), which is known as rust a combination of iron (Fe) and copper (Cu) shavings hydrogen peroxide (H2O2), a common antiseptic carbon dioxide (CO2) gas and water vapor (H2O) in the air after a forest fire silicon dioxide (SiO2), a common chemical constituent of sand hydrogen (H2) and oxygen (O2) gases added, one after the other, to the combustion chamber of a rocket oxygen (O2), nitrogen (N2) and argon (Ar) gases as they occur naturally in the Earth's atmosphere