5005 Praxis Practice Test Practice Question
Which of the following is a pure substance?
Correct Answer: C
Rationale: A pure substance consists of only one type of particle and has a uniform composition. Sodium chloride crystals (C) are pure because they consist solely of sodium and chloride ions in a fixed ratio, forming a consistent structure.
Granite rock (A) is a mixture of various minerals, making it impure. Toothpaste (B) contains multiple ingredients, including abrasives and flavorings, which also disqualifies it as a pure substance. Sugar water (D) is a solution of sugar in water, where both components retain their individual properties, further indicating it is not a pure substance.
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