When the ________ molecules of ethanol, C2H5OH, are added to water, the ethanol molecules ________.
当乙醇________分子 C 2 H 5 OH 加入水中时，乙醇分子会________。

Question

BlackTom AI · Accepted Answer

Ethanol is a polar molecule because its hydroxyl (–OH) group creates a region of partial negative charge on oxygen and partial positive charge on the hydrogen, so the ethanol molecules form hydrogen bonds with water.

1) Relevant knowledge points and concepts
- Electronegativity: oxygen (≈3.4) is much more electronegative than hydrogen (≈2.2) and carbon (≈2.5), so the O–H bond is strongly polar.  
- Hydrogen bonding: a hydrogen covalently bound to a highly electronegative atom (O) can interact with lone pairs on other O (or N, F) atoms to form hydrogen bonds.  
- Solubility and intermolecular forces: “like dissolves like” — polar solvents mix with polar solutes via dipole–dipole interactions and hydrogen bonds.

2) Step-by-step reasoning
- Step 1: Identify functional group. Ethanol is C2H5OH; the –OH (hydroxyl) is the polar functional group.  
- Step 2: Determine polarity. The O–H bond is polarized (O partial negative, H partial positive) because of the electronegativity difference (≈1.2–1.4 on the Pauling scale). This gives ethanol an overall dipole moment.  
- Step 3: Interaction with water. Water molecules also have O with lone pairs and polar O–H bonds. The partially positive H on ethanol can hydrogen-bond to a lone pair on a water O, and the lone pairs on ethanol’s O can accept hydrogen bonds from water’s H.  
- Step 4: Consequence. These mutual hydrogen bonds stabilize ethanol in aqueous solution and explain ethanol’s miscibility with water.

3) Intermediate “calculations”
- Qualitative charge separation: O (3.4) − H (2.2) ≈ 1.2 → significant polarity in O–H bond. No numerical algebraic computation is needed beyond recognizing this difference.

4) Why the correct answer is correct
- Because ethanol contains a polar O–H group, ethanol molecules are polar and can both donate and accept hydrogen bonds with polar water molecules, producing strong intermolecular attraction and mixing.

5) Why other possible alternatives are incorrect
- “Nonpolar” would be wrong because the O–H bond creates a dipole.  
- “Ionic/dissociate” is wrong because ethanol does not ionize in water under normal conditions.  
- “Only London dispersion interactions” is wrong because hydrogen bonding and dipole interactions dominate ethanol–water interactions.

Conclusion: Therefore the correct completion is: ethanol molecules are polar and form hydrogen bonds with the polar water molecules, which matches the provided answer.

When the molecules of ethanol, C2H5OH, are added to water, the ethanol molecules . 当乙醇分子 C 2 H 5 OH 加入水中时，乙醇分子会。单项选择题

类似问题

How many hydrogen bonds could the non-steroidal anti-inflammatory drug (NSAID) naproxen theoretically participate in at the same time? A. 2 B. 4 C. 5 D. 7

How many hydrogen bonds could the non-steroidal anti-inflammatory drug (NSAID) naproxen theoretically participate in at the same time? A. 2 B. 4 C. 5 D. 7

Which of the following statement about Hydrogen bonds is correct?

Which of the following statement about Hydrogen bonds is correct?

Which of the following statement about Hydrogen bonds is correct?

The unique properties of water are due to the _ of water molecules and the ability of water to form _ with other water molecules and with other polar molecules.

Each water molecule can hydrogen bond with ________ other water molecules

Which of the following statements is true for an ether?

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When the ________ molecules of ethanol, C2H5OH, are added to water, the ethanol molecules ________. 当乙醇________分子 C 2 H 5 OH 加入水中时，乙醇分子会________。单项选择题

类似问题

How many hydrogen bonds could the non-steroidal anti-inflammatory drug (NSAID) naproxen theoretically participate in at the same time? A. 2 B. 4 C. 5 D. 7

How many hydrogen bonds could the non-steroidal anti-inflammatory drug (NSAID) naproxen theoretically participate in at the same time? A. 2 B. 4 C. 5 D. 7

Which of the following statement about Hydrogen bonds is correct?

Which of the following statement about Hydrogen bonds is correct?

Which of the following statement about Hydrogen bonds is correct?

The unique properties of water are due to the ___ of water molecules and the ability of water to form ___ with other water molecules and with other polar molecules.

Each water molecule can hydrogen bond with ________ other water molecules

Which of the following statements is true for an ether?

更多留学生实用工具

希望你的学习变得更简单

When the molecules of ethanol, C2H5OH, are added to water, the ethanol molecules . 当乙醇分子 C 2 H 5 OH 加入水中时，乙醇分子会。单项选择题

The unique properties of water are due to the _ of water molecules and the ability of water to form _ with other water molecules and with other polar molecules.