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Multiple Choice
Which of the following is a compound?
A
Air
B
NaCl
C
O2
D
Fe
Verified step by step guidance
1
Understand the definition of a compound: A compound is a substance formed when two or more different elements chemically bond together in fixed proportions.
Analyze each option: Air is a mixture of gases, not chemically bonded; O\_2 is a molecule made of only one element (oxygen), so it is an element, not a compound; Fe is a pure element (iron).
Identify NaCl as a compound because it consists of two different elements, sodium (Na) and chlorine (Cl), chemically bonded together in a fixed ratio.
Recall that compounds have distinct chemical formulas representing the fixed ratio of atoms, such as NaCl, which is sodium chloride.
Conclude that among the options, NaCl is the compound because it meets the criteria of being composed of two or more different elements chemically bonded.