實驗四 碘滴定法 預報.pdf - 實驗四 化學 107...

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實驗四 碘滴定法 化學 107 C34034067 鄭羽閎 A 1 一、 目的: 學習以碘滴定法分析漂白水中有效氯含量及未知液中的 Cu 含量。 二、原理: 在碘滴定法中,常以過量的碘鹽類 ( KI) 與分析物反應生成 I 2 ,再以 Na 2 S 2 O 3 標準液滴定,即可推算出分析物含量。而 Na 2 S 2 O 3 標準液濃度的標定是以精確 量的 KIO 3 和過量的 KI 反應而生成 I 2 ,生成的 I 2 再以 Na 2 S 2 O 3 標準液滴定,即可 推算 Na 2 S 2 O 3 標準液濃度。其反應如下: KIO 3 +5KI+6H + →3I 2 +3H 2 O I 2 +2Na 2 S 2 O 3 →2NaI+Na 2 S 4 O 6 待測物:漂白水中有效成分為次氯酸鈉 (NaOCl) ,當將溶液酸化即可放釋放出 游離氯,游離氯可與碘離子作用,將產生的碘以 Na 2 S 4 O 6 標準液滴定,即可計 算漂白水中有效氯的含量。 NaOCl+2H + →Ca 2+ +Cl 2 +H 2 O Cl 2 +2I - →2Cl - +I 2 而分析未知液 Cu 含量時:銅離子若碘離子共存,銅離子將被還原為亞銅離子, 碘離子則氧化為元素態的碘,並生成白色的 CuI 沉澱,再以 Na 2 S 2 O 3 標準液滴 定生成的 I 2 ,即可推算銅含量。 2Cu 2+ +4I - →2CuI (s) +I 2 三、試劑: Na 2 S 2 O 3 ‧5H 2 O (S) Na 2 CO 3(S) KI (S) KIO 3(S) 漂白水 澱粉試劑 6N H 2 SO 4 KSCN (s) 石蕊試紙 6N 醋酸
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四、實驗步驟: 《配製 Na 2 S 2 O 3 溶液》 1. 煮沸 300ml 去離子水,蓋上錶玻璃,靜置冷卻至室溫。 2. 用秤量瓶秤取 3.1 g Na 2 S 2 O 3 ‧5H 2 O
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  • Fall '14

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