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:

1. Recall the definitions: A pure substance is either an element (composed of only one type of atom) or a compound (composed of two or more elements chemically combined in a fixed ratio). An impure substance is a mixture (composed of two or more substances physically mixed, not chemically combined).
2. Analyze the formula \( \text{Be}_3\text{Al}_2(\text{SiO}_3)_6 \): It contains multiple elements (Be, Al, Si, O) chemically combined in a fixed ratio, so it is a compound.
3. Evaluate each option:

• Option 1: A compound is a pure substance, so this is correct.
• Option 2: It is not an element (has multiple elements), so incorrect.
• Option 3: Chemical combination means pure (compound), not impure, so incorrect.
• Option 4: It is a compound (pure), not a mixture (impure), so incorrect.

Answer:

a pure substance because it is a compound.