问题 问答题

在我国青海湖地区有一种说法:冬天捞碱,夏天晒盐.这里的碱是指Na2CO3,盐是指NaCl.人们从盐湖中捞得的Na2CO3会含有少量的NaCl.

某研究性学习小组称取含NaCl的Na2CO3固体25.0g,将其配制成溶液,再向其中逐滴加入足量的7.3%的稀盐酸,使气体完全放出,共收集到8.8g CO2气体.

(1)计算原固体中Na2CO3的质量分数和消耗盐酸的总质量.

(2)下表为研究性学习小组向上述所配制的混合液中分三次逐滴加盐酸后,所记录的部分数据.

经查阅资料知:Na2CO3+HCl=NaCl+NaHCO3 (1)NaHCO3+HCl=NaCl+H2O+CO2↑(2)

已知:反应(1)完全后,反应(2)才开始.

①请完成表格中未填的部分.

实验次序每次产生的CO2的质量(g)
第一次先逐滴加盐酸100g______
第二次再逐滴加盐酸100g     8.8
第三次再逐滴加盐酸100g      0
②根据表中数据在坐标系中画出CO2质量(纵坐标)与所加入盐酸质量(横坐标)的关系图.

答案

(1)设原固体中Na2CO3的质量为x,消耗稀盐酸的质量为y

Na2CO3+2HCl=2NaCl+CO2↑+H2

106    73         44

x    y×7.3%     8.8g 

106
x
=
73
y×7.3%
=
44
8.8g

x=21.2g      y=200g

原固体中Na2CO3的质量分数=

21.2g
25.0g
×100%=84.8%

答:原固体中Na2CO3的质量分数为84.8%,消耗盐酸的总质量为200g.

(2)设溶液中21.2g碳酸钠完成反应,需要稀盐酸质量为a,生成碳酸氢钠的质量为b

Na2CO3+HCl=NaCl+NaHCO3

106   36.5       84

21.2g  a×7.3%   b

106
21.2g
=
36.5
a×7.3%
=
84
b

a=100g   b=16.8g

因此,第一次加入的100g稀盐酸恰好与碳酸钠溶液完全反应形成碳酸氢钠,该过程中没有二氧化碳放出;

设16.8g碳酸氢钠完成反应需要稀盐酸的质量为m,放出二氧化碳的质量为n

NaHCO3+HCl=NaCl+H2O+CO2

84    36.5          44

16.8g m×7.3%       n

84
16.8g
=
36.5
m×7.3%
=
44
n

m=100g  n=8.8g

因此第二次加入100g稀盐酸时开始放出二氧化碳且完全反应后碳酸氢钠反应完,最终放出二氧化碳质量为8.8g;所以第三次加入稀盐酸不再发生反应;

故答案为:①0;

阅读理解

New York, 10 November—5:27pm,yesterday. Biggest power failure in the city's

history.

 Thousands of people got stuck in lifts. Martin Saltzman spent three hours between the 21st and 22nd floors of the Empire State Building. “There were twelve of us. But no one panicked. We passed the time telling stories and playing word games. One man wanted to smoke but we didn't let him. Firemen finally got us out.”

“It was the best night we've ever had,”said Angela Carraro,who runs an Italian restaurant on 42nd Street.“We had lots of candles on the tables and the waiters were carrying candles on their trays. The place was full—and all night, in fact, for after we had closed, we let the people stay on and spend the night here.”

The zoos had their problems like everyone else. Keepers worked through the night. They used blankets to keep flying squirrels and small monkeys warm. While zoos had problems keeping warm, supermarkets had problems keeping cool.“All of our ice cream and frozen foods melted,” said the manager of a store in downtown Manhattan.“They were worth $50,000.”

   The big electric clock in the lobby(大厅)of the WaldorfAstoria Hotel in downtown Manhattan started ticking(滴答) again at 5:25 this morning. It was almost

on time.

1.Throughout the period of darkness, Martin Saltzman and the eleven others were  ________ .

A. nervous          B. excited          C. calm      D. frightened 

2.In what way was the night of November 9 the best night for Angela Carraro?

A. She had a taste of adventure.

B. Burning candles brightened the place.

C. Business was better than usual.

D. Many people stayed the night in her restaurant. 

3.How long did the power failure last?

A. Nearly 12 hours.                   B. More than 12 hours.

C. Nearly 24 hours.                   D. More than 24 hours. 

单项选择题 A1/A2型题