问题 问答题

花匠用熟石灰来降低校园苗圃中土壤的酸性,但效果不明显.化学老师发现原因是熟石灰已经部分变质,他觉得这是一个很好的实际例子,就取回一包熟石灰样品,要求学生设计实验证明该样品确实部分变质.请填写有关实验仪器和药品,完成实验报告.

【实验目的】证明熟石灰样品部分变质

【实验仪器】玻棒、胶头滴管、__________________________

【实验药品】水、酚酞试液、____________________________

实验步骤实验现象实验结论
样品中有氢氧化钙存在
样品中有碳酸钙存在

答案

由于证明氢氧化钙的存在一般在溶液中进行反应,得首先把样品溶解,故选用的仪器还有烧杯(或试管等反应容器);

证明碳酸钙的存在一般可选用酸溶液,故可选用的试剂是稀盐酸.

由题意可知样品中有氢氧化钙和碳酸钙,而氢氧化钙的水溶液可使酚酞试液变红,而碳酸钙能和稀盐酸反应生成二氧化碳气体故答案为:

在一洁净的试管中加入少量的样品,加水,搅拌,滴几滴无色酚酞试液酚酞变红
另取少量样品于一洁净试管中,滴加少量的稀盐酸有气泡产生

单项选择题

Martin Luther King, Jr., is well known for his work in civil rights and for his many famous speeches, among them his moving "I Have A Dream" speech. But fewer people know much about King’s childhood. M. L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather, the Reverend A. D. Williams, purchased their home on Auburn Avenue in 1909, 20 years before M. L. was born. The Reverend Williams, an eloquent speaker, played an important role in the community since so many people’s lives centered around the church. He allowed his church and his home to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in this atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it.
M. L.’s childhood was not especially eventful. His father was a minister and his mother was a musician. He was the second of three children, and he attended all-black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was the main artery through a prosperous neighborhood that had come to symbolize achievement for Atlanta’s black people. It was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers and other black-owned or black-operated businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a seemingly insurmountable barrier that kept black Atlantans from mingling with whites.

According to the author, King was influenced by ______.

A.community spirit

B.black lawyers

C.his mother

D.his speeches

单项选择题