✔ 最佳答案
Firstly, I guess this was an AL/AS experiment on the formation of hydrogen bonds. Secondly, I guess that the compound is 1,1,1-trichloroethane, but not 1,1,1-trichloromethane.
The formation of hydrogen bonds is a physical change, but not a chemical reaction. A hydrogen bond is formed between two identical or different molecules. One of the molecules contains an H atom which is positive enough, and the other molecule contains a highly electronegative atom (F, O or N) which is negative enough.
Trichlorochloromethane has the structural formula CHCl3, while 1,1,1-trichloroethane has the structural formula CH3CCl3. The H atom in CHCl3 is positive enough.
When trichloromethane and ethyl ethanoate are mixed, the H atoms in trichloromethane molecules and the O atoms in the C=O groups of the ethyl ethanoate molecules form hydrogen bonds, which are strong intermolecular force. The formation of hydrogen bonds is an exothermic process, and the heat evolved can increase the temperature of the mixture.
When 1,1,1-trichloroethane and ethyl ethanoate are mixed, no hydrogen bonds would be formed. Therefore, the energy change is not significant.
2008-02-28 11:04:11 補充：
The last sentence in the green paragraph should be :
"The H atom in CHCl3 is positive enough to form a hydrogen bond, but the H atoms in CH3CCl3 is not. This is because there is only one H atom in CHCl3, and it is closer to the three electronegative Cl atoms."
