问题 问答题

为测定某NaCl、Na2CO3固体混合物的组成,小明同学取16g该混合物样品放入烧杯中,称得烧杯及所盛固体混合物的总质量为98g,再把100g稀盐酸分四次平均分成四份依次加入盛有固体样品的烧杯中,每次都充分反应.实验数据如:

加入稀盐酸的次数第一次第二次第三次第四次
烧杯及反应后混合物的总质量/g121.4144.8168.6193.6
请分析以上数据后计算:

(1)第一次加入稀盐酸充分反应后,生成二氧化碳的质量是______g.

(2)该固体混合物中碳酸钠的质量分数?

(3)根据实验数据,在右边的坐标纸上绘制出所加稀盐酸质量与生成气体质量关系的曲线(不要求写出计算过程,只画出曲线即可)

答案

(1)设:样品中碳酸钠的质量分数为X;

 Na2CO3+2HCl═2NaCl+H2O+CO2

  106                   44

16g×X                  4.4g           

列比例求出X=66.25%     

(2)每25g的稀盐酸与足量的样品反应生成二氧化碳1.6g,生成4.4g的二氧化碳所需稀盐酸的质量为Y;

列比例:1.6g/25g=4.4g/Y

解得Y=68.8g    

(3)如图红线所示:根据计算68.8g的稀盐酸与碳酸钠恰好完全反应生成4.4g的二氧化碳,当加入稀盐酸超过68.8g后,碳酸钠已经完全反应,二氧化碳气体的质量不再变化.

故答案为:(1)1.6g

(2)66.25%

(3)见图红线部分.

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。

A

Knowing how much her own children loved presents at Christmas, Ann Sutton always tried to seek help for one or two poor families. With a social worker mother, the Sutton children had inherited her commitment to service, and knew never to take their good fortune at Christmas for granted.  This year, Kinzie, her seven-year-old daughter was thrilled that Santa Claus would make a special visit to a 22-year-old mother named Ashley who worked in a factory raising her 12-month-old son by herself.

The phone rang on Sunday. A representative from a local organization was calling to say that the aid Ann had requested for Ashley had fallen through. No Santa Claus, no presents, nothing.

Ann saw the cheer vanish from her children’s faces at the news. Without a word, Kinzie ran into her bedroom. She returned, her face set with determination. Opening up her piggy bank, she put all the coins onto the table: $3.30. Everything she had.

“Mom,” she told Ann, “I know it’s not much. But maybe this will buy a present for the baby.”

At a breakfast meeting the next day, Ann told her coworkers about her daughter’s story. To her surprise, staff members began to open their purses and empty their pockets to help Kinzie. By day’s end, the story of Kinzie’s gift had spread beyond Ann’s office. She received a call from an unknown donor. If a seven-year-old could give everything she had, he said, he should at least match her gift 100 to 1. He contributed $300.

On Christmas Eve, Ann drove through the pouring rain to the small trailer where the Ashleys lived. Then she began to unload the gifts from the car, handing them to Ashley one by one.

Ashley was very moved. Reflecting on a little girl’s generosity, Ashley says she’ll one day be able to do something similar for someone else in need. “Kinzie could have used that money for herself, but she gave it away,” Ashley says. “She’s the type of kid I’d like my son to grow up to be.”

56. According to the text, Ann Sutton ______________.

A. is making lots of money

B. is ready to help others

C. is only caring about herself

D. is a hard-working mother

57. Which of the following is NOT true according to the text?

A. Ashley lived a hard life with her little son.

B. The Sutton children took Anne as an example to follow.

C. The coworkers of Ann helped Kinzie to realize her wish.

D. Ann Sutton tried to ask for help for her own children.

58. What can we learn about Kinzie?

A. She was afraid that Santa Claus would visit the Ashleys.

B. She should get some presents from her mother at Christmas.

C. She devoted all her coins to buying a present for the baby.

D. She was cheerful when hearing the aid had fallen through.

59. Which of the following can be inferred from the text?

A. It rained heavily on Christmas Eve.

B. Ann handed gifts to Ashley one by one.

C. Ashley hoped she would help someone else in need.

D. A good deed can influence many people’s behavior.

60. What would be the best title for the text?

A. A Young Girl’s Gift

B. A Mother’s Love

C. A Story of Young Girl

D. An Unknown Donor

单项选择题