MCAT General Chemistry Question 264: Answer and Explanation

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Question: 264

1. The addition of which of the following substances is most likely to result in the melting of a sample during lyophilization?

A. (CH₃)₂CHOH
B. CH₃CH₂COOH
C. CH₃CH₂OCH₂CH₃
D. CH₃(CH₂)₄OH

Correct Answer: C

Explanation:

C The passage states that volatile chemicals cannot be used in samples subjected to lyophilization because they will hinder sublimation and favor the liquid phase through melting. This is because these compounds have a high vapor pressure and cannot be removed from the system by the condenser. Choices A, B, and D are all hydrogen donors and acceptors. Choice C, diethyl ether, can only act as a hydrogen bond acceptor. Therefore, it has the weakest intermolecular forces and is the most volatile.

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