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Multiple Choice
Which of the following is NOT a compound?
A
H2O
B
CO2
C
O2
D
NaCl
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.
Examine each option to determine if it consists of different elements chemically bonded:
H2O (water) consists of hydrogen and oxygen atoms chemically bonded, so it is a compound.
CO2 (carbon dioxide) consists of carbon and oxygen atoms chemically bonded, so it is a compound.
NaCl (sodium chloride) consists of sodium and chlorine atoms chemically bonded, so it is a compound.
O2 (oxygen gas) consists of only one type of element (oxygen) bonded to itself, so it is a molecule but not a compound.