Water (H20) is a liquid at room temperature and atmospheric pressure whereas hydrogen sulfide (H2S) is a gas under the same conditions. Based on this information, what can you say about the intermolecular interactions in these two substances.
So would this have to do with liquids having short-range ordering, whereas gases have long-range ordering? Thanks
No. It has all to do with hydrogen bonding. That occurs with O, N, and F.
HF has a much higher boiling point(higher than expected) than HCl; NH3 has a much higher boiling point (higher than expected) than PH3, and H2O has a much high boiling point (higher than expected) than H2S. Since H2S is a gas at room T you would expect H2O to be a gas also. But H2O is so much higher boiling that it is a liquid at room T.
The difference in physical states of water (H2O) and hydrogen sulfide (H2S) at room temperature and atmospheric pressure can be attributed to the intermolecular interactions in these substances.
In water, the hydrogen bonds between water molecules are responsible for its unique properties. Hydrogen bonds occur due to the highly electronegative oxygen atom in one water molecule attracting the hydrogen atom in a neighboring water molecule. These hydrogen bonds are relatively strong and contribute to the high boiling point and surface tension of water. As a result, water exists as a liquid at room temperature.
On the other hand, hydrogen sulfide lacks strong intermolecular interactions like hydrogen bonding. Instead, it exhibits weaker London dispersion forces, which result from temporary fluctuations in electron distribution within molecules. These dispersion forces are generally weaker than hydrogen bonds and do not provide significant attractive forces between hydrogen sulfide molecules. As a result, hydrogen sulfide exists as a gas at room temperature and atmospheric pressure.
Regarding your question about short-range and long-range ordering, it is a slightly different concept related to the arrangement of particles in a substance. Short-range ordering refers to the regular arrangement of particles within a small region, such as in a solid material with a crystalline structure. Long-range ordering, on the other hand, refers to the regular arrangement of particles spanning over a larger distance, such as in a liquid or gas.
In the case of water, the presence of hydrogen bonding allows for some degree of short-range ordering, leading to a certain level of organization among neighboring molecules. This results in the formation of clusters or small groups of water molecules. However, water molecules are not rigidly locked into fixed positions like in a solid, and they can move relatively freely, allowing for liquid-like behavior.
In the case of hydrogen sulfide, as a gas, it doesn't exhibit significant short-range or long-range ordering. The relatively weak dispersion forces between hydrogen sulfide molecules are not sufficient to maintain any significant organization or structure over long distances compared to the more pronounced interactions in a liquid or solid.
So, to summarize, the intermolecular interactions in water, particularly the presence of hydrogen bonding, contribute to its liquid state at room temperature and atmospheric pressure. In contrast, the relatively weaker dispersion forces in hydrogen sulfide result in a gas state under the same conditions.