Question

question 1 which of the following is a compound? phosphorus trichloride (pci) hydrogen gas (h2) lake water fish

Explanation:

1. Recall the definition of a compound: a substance made of two or more different elements chemically bonded together.
2. Analyze each option:

• Phosphorus trichloride (PCl₃, note: likely a typo in the question as PCl should be PCl₃) is made of phosphorus (P) and chlorine (Cl) atoms, chemically bonded, so it's a compound.
• Hydrogen gas (H₂) is a diatomic molecule of the same element (hydrogen), so it's an element, not a compound.
• Lake water is a mixture (contains water, dissolved salts, etc.), not a pure compound.
• Fish is a living organism, a complex mixture of various substances, not a compound.

Answer:

A. Phosphorus trichloride (PCl) (Note: Correct formula should be PCl₃, but among the given options, this is the compound as it consists of different elements chemically combined)