Which choice can be classified as a pure substance?

Answer 1

A pure substance can be classified as a substance that consists of only one type of atom or molecule.

Choices that can be classified as pure substances include:

1. Oxygen gas (O2): An example of a pure substance as it consists of a molecule comprising only oxygen atoms.

2. Sodium chloride (NaCl): Another example of a pure substance as it consists of a compound made up of only sodium and chloride ions.

3. Gold (Au): A pure substance as it consists of only gold atoms.

4. Water (H2O): A pure substance as it consists of a molecule made up of hydrogen and oxygen atoms in a fixed ratio.

These choices represent examples where the substance has a definite chemical composition and is considered pure because its properties are consistent and uniform throughout.