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Multiple Choice
Which of the following substances is classified as a compound?
A
Fe
B
NaCl
C
O_2
D
Air
Verified step by step guidance
1
Step 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.
Step 2: Identify each substance given in the problem: Fe (iron) is a pure element, O_2 (oxygen gas) is a molecule made of two atoms of the same element, Air is a mixture of different gases, and NaCl (sodium chloride) is made of sodium and chlorine atoms chemically bonded.
Step 3: Recognize that Fe and O_2 are not compounds because they consist of only one type of element, either as atoms or molecules.
Step 4: Understand that air is a mixture, not a compound, because its components are not chemically bonded but physically mixed.
Step 5: Conclude that NaCl is a compound because it consists of two different elements chemically combined in a fixed ratio.