A laboratory technician analyzes an unknown white crystalline solid, Sample X, to determine its classification as a pure substance or a mixture. Under constant atmospheric pressure, Sample X melts sharply at exactly 186 °C rather than over a temperature range. When heated strongly to a higher temperature in an inert environment, Sample X decomposes irreversibly into black solid carbon and water vapor. Based on these experimental observations, which conclusion correctly classifies Sample X?

A) It is a homogeneous mixture because it has a uniform appearance and separates into different substances when heated.

B) It is an element because pure substances that have a sharp melting point cannot be decomposed under any conditions.

C) It is a heterogeneous mixture because heating ultimately produces two distinct physical phases.

D) It is a compound because it exhibits a sharp melting point characteristic of a pure substance and decomposes chemically into simpler substances.

Pure substances and mixtures Transitional Reasoning Download PDF

Chemistry · Matter · Chemistry · Classification of Matter

1 Chemistry practice questions on Pure substances and mixtures. Questions that build towards applied reasoning.

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