文档介绍：1实验十一四氧化三铅组成的测定 School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 2一、实验目的?1、了解测定四氧化三铅组成的原理。?2、进一步练习滴定操作。?3、学习用 EDTA 测定溶液中的金属离子。 School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 3 ?1、化学式: Pb 3O 4,可写成 2PbO · PbO 2。?2、 Pb 30 4的分解: Pb 3O 4 + 4HNO 3 == PbO 2↓+ 2Pb(NO 3) 2 + 2H 2O 二、实验原理 School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 4 ?3、 Pb (Ⅱ)含量的测定: ? Pb 2+的量可通过 EDTA(Y 4-)滴定法求得 Pb 2+ +Y 4- == PbY 2- ?4、 PbO 2 含量的测定?PbO 2 +4I - + 4HAc = = PbI 2 +I 2+2H 2 O + 4Ac - ? I 2 + 2 Na 2S 2O 3 == 2NaI + Na 2S 4O 6 School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 5三、预习要求?1、四氧化三铅的组成及有关性质。?为红色粉末状固体,俗称“铅丹”或“红丹”, 有 2/3 的 Pb( Ⅱ)和 1/3 的 Pb( Ⅳ) ,与酸反应。?2、滴定操作要点。?指示剂加入时机和用量; 缓冲溶液控制 pH 值; ?试剂加入次序; 准确判断终点。?3、能否用其它酸如 H 2 SO 4或 HCl 溶液使 Pb 3O 4 分解?为什么? ? PbSO 4 ↓; PbCl 2 ↓, Cl 2↑。 School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 6四、实验内容? Pb 3O 4 2cm 3 6MHNO3 注意: 用蒸馏水(V 水≈ 3 V 沉淀)洗涤固体 3-4 次, 保留滤液和固体供下面的实验用。棕黑色↓水浴微热离心试管离心沉降洗↓ 3次①清液 Pb 2+(锥形瓶) ②固体 PbO 2 1、 Pb 3O 4的分解标准溶液浓度: c EDTA = 0. mol ? dm -3 c Na2S2O3 = 0. mol ? dm -3 School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 7 ?清液 Pb 2+ (锥形瓶) 1:1 的氨水 20% 的六亚甲基四胺过量 5 cm 3 , pH5~6 黄色+4~6d 二甲酚橙 6 M, <2cm 32、 Pb (Ⅱ)含量的测定橙色 20% 的六亚甲基四胺 10 cm 3? ( 去年数据)左右紫红色或橙红色 EDTA 标准液滴定紫红(澄清)粉红(浑浊)1记下 V EDTA 亮黄(澄清) School of Chemistry and Chemical Engineering, University of Jinan School of Chemistry and Chemical Engineering, University of Jinan 8 (1)取 25~ 30 cm 3 HAc-NaAc 缓冲溶液,将离心试管中的固体 PbO 2分次转入另一锥形瓶中; (