问题 问答题

学习碳酸盐知识时,老师做碳酸钠溶液和澄清石灰水反应演示实验,并对混浊液过滤,得到澄清滤液.课堂上老师的提问和学生的回答如下.师:滤液里可能含有哪些溶质呢?

甲:可能含有NaOH和Na2CO3

乙:应该含有NaOH、Na2CO3、Ca(OH)2

丙:可能恰好完全反应,只含有NaOH

(1)请你提出一个与甲乙丙同学不同的猜想:______

并对你的猜想设计一个简单的实验加以证明.

实验步骤实验现象实验结论
取样于试管中加入____________自己的猜想成立
(2)你认为甲乙丙同学的猜想谁不合理,说明理由______.

(3)甲同学针对自己的猜想进行了如下实验

实验步骤实验现象实验结论
实验1取样于试管中,滴几滴稀盐酸没有气体产生甲的猜想不成立
实验2取样于试管中,滴几滴澄清石灰水溶液变混浊甲的猜想成立
请说明甲同学的两个实验设计是否正确?说明理由

实验1______;实验2______

写出实验2所发生反应的化学方程式:______.

答案

(1)碳酸钠溶液和澄清石灰水发生反应,若恰好完全反应,所得溶液中溶质为氢氧化钠溶液;若反应中碳酸钠有剩余,所得溶液中溶质则为氢氧化钠与碳酸钠;若反应中氢氧化钙溶液有剩余,所得溶液则为氢氧化钠溶液与氢氧化钙的混合溶液;其它两种可能已被另两位同学做了猜想,所以,我的猜想只能为:氢氧化钠溶液与氢氧化钙溶液的混合物;

氢氧化钠和氢氧化钙同属于碱,其化学性质很相似,但在发生反应时的现象却因金属离子的不同而不同;如与气体二氧化碳反应时,氢氧化钙能形成沉淀而氢氧化钠与二氧化碳因生成可溶性的碳酸钠而无明显现象;因此可利用变化时现象的不同,证明氢氧化钙的存在;

(2)乙同学在进行猜想时,没有考虑到碳酸钠和氢氧化钙都有剩余时,反应还会继续进行;因此,猜想错误;

故答案为:小芳同学的猜想不合理.因为Na2CO3与Ca(OH)2要发生反应,不可能共存.

(3)向氢氧化钠溶液与碳酸钠溶液的混合溶液中滴加少量稀盐酸时,稀盐酸与碳酸钠反应产生的少量气体会被氢氧化钠吸收而观察不到有气体放出,因此,滴加少量稀盐酸看不到气泡不能得到溶液不含碳酸钠的结论;

氢氧化钠与碳酸钠不反应,而氢氧化钙与碳酸钠可反应生成沉淀,反应方程式是Na2CO3+Ca(OH)2═2NaOH+CaCO3↓;故可通过滴加石灰水观察是否变浑浊判断是否含有碳酸钠;

故答案为:(1)可能含有NaOH和Ca(OH)2

实验步骤实验现象实验结论
通入二氧化碳出现白色浑浊 
(2)乙同学的猜想不合理.因为Na2CO3与Ca(OH)2要发生反应,不可能共存;

(3)不正确.有NaOH存在,就不会有CO2气体放出,但Na2CO3可能存在;正确.氢氧化钠与碳酸钠不反应,碳酸钠可与氢氧化钙反应生成碳酸钙沉淀;

Na2CO3+Ca(OH)2═2NaOH+CaCO3↓.

阅读理解

第三部分:阅读理解(共20小题;每小题2分,满分40分)

阅读下列短文,从每题所给的四个选项(A、B、C、D)中选出最佳选项,并在答题卡上将该项涂黑。

Harvard University is on the both sides of the Charles River. The oldest institution of higher learning in the United States was founded in 1636. In 1638 it was named for John Harvard, its first founder. During the 1640s the college was enlarged although it was short of money. Meant to be an institution for the educatiou of Puritan ministers (清教牧师), it grew to be an institution of general education, and new and more subjects and policies (政策) were introduced. In the 18th century, particularly under John Leverett, the number of the students and campus equipment increased while the religious (宗教的) color decreased. In its early years, the college was largely supported by the English colony and the New England community as a whole, but support soon came in the form of gifts, and in 1823 the state money was received for the last time. Under Charles W. Eliot, the college became a great modem university. Its basic courses improved and enlarged, the graduate school was set up for those who finished their four-year undergraduate study, and the law and medical schools were reorganized. Eliot is also famous for his introduction of the elective system at Harvard. Besides Harvard College, the university includes schools of divinity (1816), law (1817), arts and science (1872), education (1920), engineering (1935), reorganization of Lawrence Science School of 1847, public administration (1935). Harvard also has schools of business administration (1908), medicine (1782), public health (1922), and dental health ( 1941 ). Radcliffe College for women is connected with Harvard; its students are taught by Harvard professors and receive diplomas given by Harvard. The university library, among the nation's finest houses over 8 mil- lion volumes, and the Fogg Museum of Art is one of the finest university museums in the world. Harvard is closely connected with a large number of research institutions as well.

56. Harvard University

A. has a history of more than 450 years

B. was enlarged in the middle of the 17th century 

C. was first meant to be an institution for general education since its foundation

D. was founded by John Leverett

57. One of John Leverett's greatest contributions to Harvard University is most probably that

A. he set up Harvard University

B. he freed Harvard University from the support of the state

C. he made Harvard a Puritan university

D. he helped develop general education in Harvard University

58. Which of the following statements might NOT be true about Charles W. Eliot?

A. Under his leadership, Harvard University became a modern university.

B. He introduced the elective system at Harvard University.

C. He improved and enlarged Harvard University, making it a modern university.

D. He tried hard to reduce the religious colour of Harvard University.

59. Which of the following statements is true about Harvard University according to the passage?

A. Harvard is a large and modern university with a long history.

B. Harvard has the world's finest library with its 8 million of books.

C. Harvard University has the nation's best art museum.

D. Radcliffe College for men is one of the schools of Harvard University.

名词解释