题目

There was a king who loved art very much. One day a(n)  41  came and said, Please let me  42 a picture on a wall. The king happened to have a big new hall  43  . So he  44  the artist to work on one of the walls. At the same time, another artist came and asked to work on the  45  wall. He promised he would make the same picture as the first artist’s  46  looking at the first artist’s work. The second artist asked to have a thick curtain  47  between the two walls  48  neither of them could see each other. The following day they began to work. The first artist brou18．氯酸镁[Mg（ClO3）2]常用作催熟剂、除草剂等，实验室制备少量Mg（ClO3）2•6H2O的流程如下：已知：①卤块主要成分为MgCl2•6H2O，含有MgSO4、FeCl2等杂质．②几种化合物的溶解度（S）随温度（T）变化曲线如图所示．（1）过滤所需要的主要玻璃仪器有漏斗、玻璃棒、烧杯，加MgO后过滤所得滤渣的主要成分为BaSO4和Fe（OH）3．（2）加入BaCl2的目的是除去SO42-，如何检验SO42-已沉淀完全？答：静置，取上层清液加入BaCl2，若无白色沉淀，则SO42-沉淀完全．（3）加入NaClO3饱和溶液发生反应为：MgCl2+2NaClO3═Mg（ClO3）2+2NaCl↓再进一步制取Mg（ClO3）2•6H2O的实验步骤依次为：①蒸发结晶；②趁热过滤；③冷却结晶；④过滤、洗涤．（4）产品中Mg（ClO3）2•6H2O含量的测定：步骤1：准确称量3.50g产品配成100mL溶液．步骤2：取10mL于锥形瓶中，加入10mL稀硫酸和20mL 1.000mol•L-1的FeSO4溶液，微热．步骤3：冷却至室温，用0.100mol•L-1 K2Cr2O7溶液滴定至终点，此过程中反应的离子方程式为：Cr2O72-+6Fe2++14H+═2Cr3++6Fe3++7H2O．步骤4：将步骤2、3重复两次，平均消耗K2Cr2O7溶液15.00mL．①写出步骤2中发生反应的离子方程式：ClO3-+6Fe2++6H+=6Fe3++Cl-+3H2O．②产品中Mg（ClO3）2•6H2O的质量分数为78.3%．