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Multiple Choice
Which of the following substances is a mixture?
A
O_2
B
Air
C
H_2O
D
NaCl
Verified step by step guidance
1
Step 1: Understand the difference between a pure substance and a mixture. A pure substance has a fixed composition and distinct properties, while a mixture contains two or more substances physically combined, each retaining its own properties.
Step 2: Identify the substances given: \(O_2\) (oxygen gas), \(H_2O\) (water), \(NaCl\) (sodium chloride), and Air.
Step 3: Recognize that \(O_2\), \(H_2O\), and \(NaCl\) are pure substances. \(O_2\) is a pure element, \(H_2O\) is a pure compound, and \(NaCl\) is an ionic compound with a fixed composition.
Step 4: Understand that Air is a mixture because it consists of several gases (mainly nitrogen, oxygen, carbon dioxide, and others) physically combined without a fixed ratio.
Step 5: Conclude that among the options, Air is the mixture, while the others are pure substances.