题目

  A quarter of today’s UK children are living in families which cause more than one risk to their educational development, a study says.    Institute of Education researchers analyzed 10 risk factors affecting more than 18,000 families. Risks included financial stress, teenage parenthood, depression, low skills and alcohol abuse. Previous research suggests families with multiple risk factors are the most damaging. According to the research, just over four in ten people experienced no risk factors in their early childhood, while a third faced only one. It would mean 192.000 UK child在古代，人们常用贝壳（主要成分是碳酸钙，杂质不参加反应且不溶于水）和纯碱为原料制取烧碱，某小组同学按图所示流程进行实验，请你参与讨论并回答相关问题．（1）贝壳高温煅烧时，发生反应的化学方程式是；（2）溶液蒸发结晶得到固体C的过程中，常用玻璃棒搅拌，其目的是；（3）【问题与发现】该小组同学所得到固体C一定是纯净的NaOH吗？【猜想与假设】根据反应原理，小组同学提出以下猜想：①纯净的NaOH；②NaOH和Na2CO3的混合物；③丙：NaOH和Ca（OH）2的混合物；④NaOH、Na2CO3和Ca（OH）2的混合物。讨论后，小组同学都认为猜想④不合理，原因是。（4）【探究与验证】小组同学设计下列方案对猜想进行验证，请参与他们的探究并完成所缺内容。实验操作现象结论实验一：取少量固体C，溶于适量水形成溶液后，滴加几滴酚酞试液溶液变红猜想①成立实验二：取少量固体C，溶于适量水形成溶液后，滴加足量无气泡产生猜想②不成立实验三：取少量固体C，溶于适量水形成溶液后，滴加几滴饱和Na2CO3溶液猜想③成立（5）【反思与评价】反思实验过程，实验一设计（填“合理”或“不合理”），原因是。