A Level Chemistry OCR Practice Exam

Which of the following best represents the term 'anhydrate'?

1. A compound that has a low melting point

2. A compound that contains water of crystallisation

3. A compound that is completely dry with no water content

4. A mixture of different hydrated forms

The correct answer is: A compound that is completely dry with no water content

The term 'anhydrate' refers to a compound that is completely dry with no water content. In chemistry, an anhydrate is typically formed by removing the water of crystallization from a hydrated compound, which contains water in its crystal structure. This process often occurs through heating, leading to the loss of water while leaving the remaining solid structure intact. In contrast, the other options describe different characteristics not applicable to anhydrates. For example, a compound with a low melting point does not inherently relate to its hydration status. Similarly, a compound that contains water of crystallization is, by definition, a hydrated compound and not an anhydrate. Lastly, a mixture of different hydrated forms suggests a combination of multiple compounds, which does not align with the singular definition of an anhydrate. Thus, the complete absence of water content defines an anhydrate accurately.