Which among the following is pure matter ? A. Carbon dioxide B. Brass C. Air D. Iron

The correct answer is: D. Iron

• Carbon dioxide is a compound made up of carbon and oxygen atoms.
• Brass is an alloy made up of copper and zinc atoms.
• Air is a mixture of gases, including nitrogen, oxygen, argon, carbon dioxide, and other trace gases.
• Iron is a pure element made up of iron atoms.

A pure substance

is a substance that is made up of only one type of atom or molecule. Iron is a pure substance because it is made up of only iron atoms. Carbon dioxide, brass, and air are not pure substances because they are made up of more than one type of atom or molecule.