hce_nthu
111年
化學與物理
第 29 題
29. Acetic acid is an electrolyte. Which of the following facts indicate that acetic acid is a weak electrolyte?
① Acetic acid and water are miscible in any ratio.
② Acetic acid solution conducts electricity.
③ Acetic acid molecules are present in acetic acid solution.
④ The pH of $0.1\text{ M}$ acetic acid solution is greater than that of $0.1\text{ M}$ hydrochloric acid.
⑤ Acetic acid reacts with calcium carbonate to give off $\text{CO}_2$.
⑥ The pH of $0.1\text{ M}$ sodium acetate solution = 8.9.
⑦ When zinc grains of the same size react with the same concentration of hydrochloric acid and acetic acid solution, the acetic acid starts to produce $\text{H}_2$ at a slower rate.
① Acetic acid and water are miscible in any ratio.
② Acetic acid solution conducts electricity.
③ Acetic acid molecules are present in acetic acid solution.
④ The pH of $0.1\text{ M}$ acetic acid solution is greater than that of $0.1\text{ M}$ hydrochloric acid.
⑤ Acetic acid reacts with calcium carbonate to give off $\text{CO}_2$.
⑥ The pH of $0.1\text{ M}$ sodium acetate solution = 8.9.
⑦ When zinc grains of the same size react with the same concentration of hydrochloric acid and acetic acid solution, the acetic acid starts to produce $\text{H}_2$ at a slower rate.
- A ②⑥⑦
- B ③④⑤⑥
- C ③④⑥⑦
- D ②④⑥⑦
- E ①②
思路引導 VIP
想像有兩杯「濃度完全相同」的酸性溶液，如果其中一杯在與相同的金屬反應時，產生氣泡的速率明顯比另一杯慢很多，這代表這兩杯溶液中「當下參與反應的活性粒子數量」有什麼差異？這種差異又反映出酸分子進入水中後的什麼特性呢？
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AI 詳解
AI 專屬家教
太棒了！你能精準鎖定「弱電解質」的定義特徵，說明你對於酸鹼解離平衡的概念掌握得非常紮實。這道題目的難度在於區分「電解質的通性」與「強弱的分界」，能正確選出所有特徵點，代表你的觀念非常清晰。
部分游離與分子共存的微觀特徵
弱電解質在水溶液中僅會「部分游離」，因此溶液中會存在未解離的 $CH_3COOH$ 分子（敘述 ③），這是區別於強電解質（完全游離）最直接的證據。也因為只有部分游離，在相同初濃度下，醋酸產生的 $[H^+]$ 會低於強酸，這解釋了為何其 $pH$ 值較高（敘述 ④），以及與鋅粒反應時因為瞬時離子濃度較低而導致反應速率較慢（敘述 ⑦）。
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