中四化學問題

Firstly, HCl is a covalent molecular compound. In pure HCl (hydrogen chloride), there are only HCl molecules, but no ions.

In aqueous solution HCl, the HCl molecules are ionized to give H^+(aq). Therefore, the aqueous solution of HCl is known as hydrochloric acid, but not hydrogen chloride.

You MUST have such idea that pure HCl is molecular, but it is ionized in water to give H^+(aq) ions when you attend HKCEE examination, esp. in Paper II MC questions. The HKCEE syllabus also includes that acids in the absence of water (e.g. dissolved in a non-polar solvent) do not show acidic properties because of their molecular structure.

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CH3COOH is a monobasic acid. This is because the C-H bonds are too strong to be broken. Only the -COOH group can release H^+(aq) ions in water, and the full explanation involves the AL syllabus.

2008-01-27 19:44:36 補充：
不要模稜兩可的說「唔一定 covalent 既」。也不要說「在 CE 程度 HCl 是 ionic」。無論 CE, AL, 甚至 U level，pure HCl 都係 covalent/molecular。唔識就語唔識，千祈唔好扮醒，最基本概念都教錯人！

2008-01-27 19:44:37 補充：
不要模稜兩可的說「唔一定 covalent 既」。也不要說「在 CE 程度 HCl 是 ionic」。無論 CE, AL, 甚至 U level，pure HCl 都係 covalent/molecular。唔識就語唔識，千祈唔好扮醒，最基本概念都教錯人！

2008-01-27 19:46:02 補充：
唔好意思，press the "enter" key a few times.

唔一定係COVALENT 既..
CE 既LEVEL 你可以話ACID係一個COMPOUND 都可以GA喇
AL 就會有個好D GE DEFINITION GA 喇.總知你知道ACID 既特性係可以react with base to form water and salt.仲有,佢dissloves in water to give H ion as the only positive ion 就OK.
仲有HCL係IONIC COMPOUND (向CE 既知識中)