【Daily Question】Theoretical Foundation 2020.07.12
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Multiple-choice question: Among the following compounds, which one has intermolecular hydrogen bonds? ( ) A. CH3Br B. NH3 C. CH4 D. CH3Cl Answer: B Hint: An additional reward will be given to those who can explain the solution process; the answer can be found in the response
Explanation for answer B: Hydrogen bonds exist between molecules that contain O–H, N–H, and F–H bonds
Elements that can form hydrogen bonds require high electronegativity and a small atomic radius; only F, O, and N meet these criteria
B 1. Ammonia contains hydrogen atoms, as well as nitrogen atoms with high electronegativity; moreover, the nitrogen atoms have lone pairs of electrons, which create the conditions necessary for hydrogen bonding to occur. 2. In its liquid state, ammonia molecules are close enough to each other to allow hydrogen bonding to take place. 3. Due to the presence of hydrogen bonds, liquid ammonia can undergo autoionization similar to water, resulting in the formation of ammonium ions and amide anions. Of course, the degree of ionization is low, and this process is reversible: 2NH3 → NH4+ + NH2-