Question

How should a sample be prepared for a Mel-Temp Melting Point Apparatus?

a) Dissolved in excess solvent
b) In powdered form
c) As a thick paste
d) As a large crystal

Answer 1

For a Mel-Temp Melting Point Apparatus, the sample must be in powdered form for even heating and accuracy. Samples in other forms like pastes, crystals, or dissolved in solvent, would lead to inaccurate melting point determinations.

Thus option b) In powdered form. is correct answer.

Step-by-step explanation:

To accurately determine the melting point using a Mel-Temp Melting Point Apparatus, a sample needs to be in powdered form. This allows the sample to pack tightly into a capillary tube, providing even heating and accurate measurement of the melting point. The sample should not be dissolved in excess solvent, as that would prevent proper determination of its melting point. It should also not be in the form of a thick paste or a large crystal because these forms can cause uneven heating and subsequently inaccurate results.

Melting points provide crucial information about the purity and identity of a compound. The enthalpy of fusion denotes the energy required to change a substance from solid to liquid at its melting point, which correlates with the strength of the intermolecular forces holding the crystal lattice together. Hence, a detailed understanding and correct preparation of the sample are essential for precise measurements.

Thus option b) In powdered form. is correct answer.

Answer 2

The sample for a Mel-Temp Melting Point Apparatus should ideally be prepared as a large crystal (d).

Step-by-step explanation:

Preparing a sample for a Mel-Temp Melting Point Apparatus involves considerations for accuracy and reliability of the melting point determination. A large crystal formation helps ensure consistent and precise results. When a substance crystallizes into a larger form, it often indicates a higher purity level, crucial for an accurate melting point determination. This is because impurities tend to disrupt crystal formation, leading to a wider melting point range.

In contrast, if the sample were dissolved in excess solvent (a), it might result in a solution with impurities dissolved within it. The impurities could affect the observed melting point, leading to inaccuracies. Powdered form (b) or a thick paste (c) can also present challenges. These forms might contain air pockets or varying degrees of compactness, influencing the observed melting point range.

The choice of a large crystal ensures uniformity and consistency in the sample structure, minimizing the impact of impurities or irregularities in the substance. It allows for a more accurate determination of the melting point, critical in identifying and characterizing substances based on their unique melting properties. Therefore, the optimal preparation for a Mel-Temp Melting Point Apparatus involves using a sample in the form of a large crystal.