问题 问答题

某化学兴趣小组到野外考察,取回一些石灰石样品(杂质不溶于水也不与稀盐酸反应).为了确定其组成,该小组做了以下实验:取石灰石8克于烧杯中,然后分四次加入稀盐酸(每次加入l0克),实验过程中所得数据如下表:

    实验次数    1    2    3    4
    加入稀盐酸质量(克)    10    10    10    10
  烧杯中余下固体质量(克)    5    m    l    1
(1)m=______;

(2)该石灰石样品中碳酸钙的质量分数;

(3)实验结束后烧杯中稀盐酸的溶质质量分数.(计算结果保留l位小数)

答案

(1)由第一次加入10g稀盐酸剩余固体可以知道,第1次反应消耗了碳酸钙3g,而到第3次剩余的为1g,所以可以判断第一次盐酸已被反应完全,且碳酸钙有剩余,所以第2次消耗的碳酸钙的质量依然为3g,即m的值为5-3=2,

(2)根据题意及表格中的数据可以知道,剩余的1g固体为杂质,即碳酸钙的质量为:8g-1g=7g,所以该石灰石样品中碳酸钙的质量分数为:

7g
8g
×100%=87.5%

(3)设10克稀盐酸中溶质质量为x,反应产生二氧化碳的质量为y

CaCO3+2HCl═CaCl2+H2O+CO2

100   73             44

3g    x              y

100
3g
=
73
x
=
44
y

解得:x=2.19g    y=1.32g

所以盐酸的质量分数为:

2.19g
10g
×100%=21.9%;

由表格中的数据可以知道每10g盐酸能够消耗3g碳酸钙,根据(1)中的分析可以知道,第一次和第二次的盐酸已被完全消耗,而第3次只有1g碳酸钙和盐酸反应,而第四次中的盐酸没有反应,所以最终剩余的盐酸的质量为:

10g
3g
×(2g+3g)=
50
3
g;

所以实验结束后烧杯中HCl的质量为:

50
3
g×21.9%=3.65g

该过

3.65g
40g-3.08g
×程中产生CO2的总质量为:
10g
1.32g
×7g=3.08g.

所以实验结束后烧杯中HCl的质量分数为:

3.65g
40g-3.08g
×100%=8.3%.

答:(1)m=2;

(2)该石灰石样品中碳酸钙的质量分数为87.5%;

(3)实验结束后烧杯中稀盐酸的溶质质量分数8.3%.

问答题 简答题
阅读理解

阅读理解。

     There are many famous museums throughout the world where people can enjoy art. Washington, D.C. has

the National Gallery of Art (美术馆); Paris has the Luvre; London, the British Museum. Florida International

University (FIU) in Miami also shows art for people to see. And it does so without a building, or even a wall for

its drawings and paintings. FIU has opened what it says is the first computer art museum in the United States.

You don'[t have to visit the University to see the art. You just need a computer linked to a telephone. You can

call the telephone number of a university computer and connect your own computer to it. All of the art is stored

in the school computer. It is computer art, produced electronically by artists on their own computers. In only a

few minutes, your computer can receive and copy all the pictures and drawings.

     Robert Shostak is director of the new computer museum. He says he starts the museum because computer

artists had no place to show their works.

     A computer artist can only record his pictures electronically and send the records, or floppy discs, to others

to see on their computers. He can also put his pictures on paper. But to print good pictures on paper, the

computer artist needs an expensive laser printer.

     Robert Shostak says the electronic museum is mostly for art or computer students at schools and universities. Many of the pictures in the museum are made by students. Mr Shostak said the FIU museum will make

computer art more fun for computer artists because more people can see it. He says artists enjoy their work

much more if they have an audience. And the great number of home computers in America could mean a huge

audience for the electronic museum.

1. The main purpose of this text is to give information about _____.

A. museums throughout the world

B. an electronic art museum in Miami, U.S.A.

C. art exhibitions in Florida International University

D. latest development of computer art

2. To see the art in FIU museum, you need _____.

A. floppy discs

B. a computer and a printer

C. pictures and drawings on paper

D. a computer connected to the museum by telephone line

3. The museum was started when _____.

A. Robert Shostak wanted to do something for computer scientists

B. Robert Shostak wanted to help computer artists

C. art students needed a place to show their works

D. computer scientists wanted to do something about art

4. The words "an audience"in the last paragraph refer to _____.

A. art students

B. computer owners

C. exhibits in the museum

D. those who will enjoy art