Draw the hydrogen bonding between two water molecules. 4 H H H 5. Draw the hydrogen bonding between a water molecule and an ethanol molecule H 5 O-H 17-0 H
The Correct Answer and Explanation is:
Here are the correct answers and a detailed explanation for the provided questions.
Correct Answers
4. Hydrogen bonding between two water molecules:
A correct drawing shows one water molecule (H₂O) oriented so that one of its partially positive hydrogen atoms points toward the partially negative oxygen atom of a second water molecule. The hydrogen bond is represented by a dashed or dotted line connecting the hydrogen of the first molecule to the oxygen of the second.
H
|
H--O-- - - - O--H
|
H
(The dashed line represents the hydrogen bond)content_copydownloadUse code with caution.
5. Hydrogen bonding between a water molecule and an ethanol molecule:
A correct drawing shows a water molecule (H₂O) and an ethanol molecule (CH₃CH₂OH). A hydrogen bond can form in two ways:
- The partially positive hydrogen from water’s -OH group is attracted to the partially negative oxygen of ethanol’s -OH group.
- The partially positive hydrogen from ethanol’s -OH group is attracted to the partially negative oxygen of water’s -OH group.
Both are correct. Below is an example of the first case:
H
|
CH₃CH₂-O-- - - - O--H
| |
H H
(The dashed line represents the hydrogen bond)content_copydownloadUse code
Explanation
A hydrogen bond is a strong type of intermolecular force, an attraction that occurs between molecules rather than within them. Its formation requires a specific set of conditions. A hydrogen atom must be covalently bonded to a highly electronegative atom—most commonly oxygen (O), nitrogen (N), or fluorine (F). This covalent bond is highly polar, meaning the electron pair is pulled strongly toward the electronegative atom. As a result, the electronegative atom gains a partial negative charge (δ-), and the hydrogen atom gains a partial positive charge (δ+).
For question 4, concerning two water molecules, this principle is clearly demonstrated. In each H₂O molecule, the oxygen atom is highly electronegative and carries a partial negative charge, while the two hydrogen atoms are partially positive. The hydrogen bond is the electrostatic attraction between a partially positive hydrogen (δ+) of one water molecule and the partially negative oxygen (δ-) of a neighboring water molecule. The drawing provided for question 4 correctly identifies this interaction between an H and an O atom, though it uses parallel lines instead of the standard dashed line notation.
For question 5, which involves a water molecule and an ethanol molecule (CH₃CH₂OH), the same logic applies. Both molecules contain a hydroxyl (-OH) group. The oxygen atom in each -OH group is partially negative, and the hydrogen atom is partially positive. Therefore, a hydrogen bond can form in two primary ways: the hydrogen from water can be attracted to the oxygen in ethanol, or the hydrogen from ethanol’s hydroxyl group can be attracted to the oxygen in water. Both interactions are valid and are the reason ethanol dissolves so well in water. The drawing for question 5 correctly shows an attraction between the oxygen of one molecule and a hydrogen of the other, demonstrating a proper understanding of the concept.
