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(每小題2分,共6分)請回答有關電解水的問題

(1)右圖為通電分解水的簡易裝置,如果用VA和VB分別表示試管A和試管B中生成氣體的體積,則VA:VB約等于      。理論上應等于此比例,實際上常大于此比例,原因之一是___________________________________

(2)A試管中電極連接的電池的_______極,B中產生的氣體是_______

(3)該實驗能證明的結論是___________________________________

 

【答案】

(1)2:1   合理給分  (2)負  O2    (3)由氫,氧元素組成。

【解析】

試題分析:依據所學化學知識和實驗經驗來解答。

根據“正氧負氫,氫二氧一”,結合圖示可推出:由于A中氣體體積較多,所以應該是氫氣,則A試管中的電極連接的電池的負極;B試管中氣體體積少,所以應該是氧氣,則B試管中電極連接的電池的正極;由于氫氣和氧氣的體積比為2:1,則VA:VB約等于2:1,由于氧氣是不易溶于水,氫氣是難溶于水,所以氧氣在水中的溶解的量較大些,因此實際上常大于此比例。

因為化學反應前后元素的種類不變,而反應生成的氫氣是由氫元素組成的,氧氣是由氧元素組成的,由此可知,水是由氫元素和氧元素組成的。

考點:電解水實驗

點評:解答本題的關鍵是明確電解水的現象,可以用“正氧負氫,氫二氧一”來分析解答。

 

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(每小題2分,共6分)請回答有關電解水的問題
(1)右圖為通電分解水的簡易裝置,如果用VA和VB分別表示試管A和試管B中生成氣體的體積,則VA:VB約等于     。理論上應等于此比例,實際上常大于此比例,原因之一是___________________________________

(2)A試管中電極連接的電池的_______極,B中產生的氣體是_______
(3)該實驗能證明的結論是___________________________________

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