题目

Whenever I recall my childhood, there is one thing I remember clearly. My father used his   36  to let my mother   37   her parents who lived far away. There was just my younger brother and myself in the   38  . One evening, our father came home and there was no   39  , not even a piece of bread. My father had no money and he was as   40   as we were. My brother and I went to bed without having anything.    41   I knew from the expressions on my father’s face that he could not    42   us be hungry for long. He left the house, and about two hours later he   43   1．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．②四种化合物的溶解度（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，（2）加入BaCl2的目的是除去SO42-或使SO42-沉淀，加MgO后过滤所得滤渣的主要成分为BaSO4和Fe（OH）3．（3）加入NaClO3饱和溶液后发生反应的化学方程式为MgCl2+2NaClO3=Mg（ClO3）2+2NaCl↓，再进一步制取Mg（ClO3）2•6H2O的实验步骤依次为：趁热过滤（将滤液）冷却结晶①蒸发结晶；②；洗涤；将分离出去，③；④过滤、洗涤．（4）产品中Mg（ClO3）2•6H2O含量的测定：（已知Mg（ClO3）2•6H2O的摩尔质量为299g/mol）步骤1：准确称量3.50g产品配成100mL溶液．步骤2：取10.00mL于锥形瓶中，加入10.00mL稀硫酸和20.00mL 1.000mol•L-1的FeSO4溶液，微热．步骤3：冷却至室温，用0.100mol/L K2Cr2O7溶液滴定剩余的Fe2+至终点．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写出步骤3中发生反应的离子方程式：Cr2O72-+6Fe2++14H+=2Cr3++6Fe3++7H2O；③产品中Mg（ClO3）2•6H2O的质量分数为78.3%．