Multiple Choice
Which two types of matter are classified as pure substances?
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1. Intro to General Chemistry
Classification of Matter
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Which of the following substances is a mixture?
A
O_2
B
Air
C
H_2O
D
NaCl
Verified step by step guidance1
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.
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