Question

the chemical formula for an emerald is be₃al₂(sio₃)₆. an emerald can be described as a pure substance because it is a compound. a pure substance because it is an element. an impure substance because it is chemically combined. an impure substance because it is a mixture.

Explanation:

A pure substance can be either an element or a compound. An element consists of only one type of atom, while a compound is made up of two or more different - types of atoms chemically combined in a fixed ratio. The chemical formula $\text{Be}_3\text{Al}_2(\text{SiO}_3)_6$ shows that emerald is a compound as it is composed of multiple elements (beryllium, aluminum, silicon, oxygen) chemically bonded together. Compounds are pure substances.

Answer:

a pure substance because it is a compound.