194 g 之 kscn 固體用去離子水稀釋至 100ml

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0.194 g KSCN 固體。用去離子水稀釋至 100ml 定量瓶 中,配成濃度 0.02 M KSCN aq 《以直接柏哈法標定 KSCN 溶液》 1. 取兩個洗淨之 300ml 錐形瓶, #1 #2 分別做兩次實驗。 2. AgNO 3 aq 的滴定管 ( 先紀錄初讀數 ) 流出約 15ml AgNO 3 於錐形瓶 中,並加入 2ml 6N HNO 3 水溶液及 2ml 鐵明礬指示劑。 3. 由裝 KSCN aq 的滴定管 ( 先紀錄初讀數 ) 小心滴入 KSCN aq ,直到溶液 轉變至紅棕色為止。若滴定過量可以使用反滴定步驟,即反覆滴定 直到找尋至正確中和點。 4. 最後記錄兩滴定管末讀數。 5. 同理,重複標定一次。 《測定未知物中 X - 的含量》 (1) 未知物溶液配置: 用秤量瓶精秤 0.18 g 之未知氯化物固體,並經確記錄重量至 0.1mg ,再用 去離子水稀釋至 250ml 定量瓶中。 (2) 間接 Volhard 法: 1. 用吸量管分別取 25.00ml 配好的氯化物溶液至 300ml 錐形瓶 #1 #2 中, 各加入 2mL 6N HNO 3 溶液。 2. 放入攪拌子,由裝 AgNO 3 aq 的滴定管滴入 20ml AgNO 3 #1 錐形瓶, 精確紀錄體積讀數。 3. 煮沸 #1 錐形瓶中 AgCl 沉澱,使其凝結成較粗大的顆粒後,過濾沉澱 AgCl 沉澱,濾液再加入 2 ml 鐵明礬指示劑,再以 KSCN 滴定 4. 濾液以 KSCN aq 滴定至溶液變成淡紅棕色,並保持 15 秒以上,此即達 滴定終點。 5. 重複上述步驟滴定 #2 錐形瓶。
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(3) Mohr 法: 1. 用吸量管分別取 25.00ml 配好之氯化物溶液至 300ml 錐形瓶 #1 #2 中。 2. 以石蕊試紙測試溶液是否呈中性;若溶液呈酸性,則加入少量碳酸鈣固 體直至呈中性。 3. 加入 0.5 ml 5% K 2 CrO 4 指示劑於 #1
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  • Fall '14

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