某品牌纯碱产品中含有少量氯化钠杂质，其产品包装袋上标明：碳酸_爱下问搜题

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问题问答题

某品牌纯碱产品中含有少量氯化钠杂质，其产品包装袋上标明：碳酸钠≥96%．为测定该产品中含碳酸钠的质量分数，进行了以下实验；取11.0g纯碱样品放入烧杯中，称得烧杯及所盛纯碱样品的总质量为158.0g，再把100g稀盐酸平均分成四份依次加入样品中，充分反应后，实验数据记录如下：

所加盐酸的次数	第一次	第二次	第三次	第四次
烧杯及所盛物质的总质量/g	181.2	204.4	228.6	253.6

请你据此分析计算：

（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）该产品中碳酸钠的质量分数？

答案

（1）由表格数据可知，第一次生成二氧化碳的质量为：158.0g+100g÷4-181.2g=1.8g；故填：1.8；

（2）充分反应后生成二氧化碳的质量为：158.0g+100g-253.6g=4.4g

设样品中含有的碳酸钠的质量为x

Na₂CO₃+2HCl=2NaCl+H₂O+CO₂↑

106 44

x 4.4g

106

x

=

44

4.4g

x=10.6g

碳酸钠的质量分数为：

10.6g

11.0g

×100%=96.4%

答：该产品中碳酸钠的质量分数为96.4%．

完形填空

My 8yearold son，Kevin，has made friends with some boys in the neighborhood. He has been 36 with them after school. My wife，and I are 37 he has other kids to be with and we have __38__ and encouraged him to play with his friends. We also want Kevin to learn __39__，so we have asked him to tell us __40__ he's going and to come home at a specified time.
The __41__ started when Kevin didn't come home on time. On one occasion，I asked Kevin to be back at 6 pm. By 6：30，I needed to go __42__ him. I found him at a friend's house，and he looked 43 that he couldn't continue playing. After we came home，I sat Kevin down for a talk about the _44 _ of keeping his word. I told him I was not worried about his arriving a few __45__ late， after a half hour， he told me he understood and I was _46_ _.
The next day，I came home from work at about 6:30 pm and my wife asked me to go and get Kevin back __47__ she said he should be back home at 6. I walked to his friend's house and a look of __48__ appeared on Kevin's face when he came to the door.
At __49__，my wife and I spoke to Kevin about why he didn't come home on time again. He said he just wanted to _50__ playing. This was __51__，so we decided to ground(罚不准出门)him for a week. This __52_ no playing with his friends.
For the next week，whenever his friends came to ask for Kevin，we let him __53__ to them that he was grounded. We felt this would help him be responsible for his __54__.
As a __55__，I believe one of the most important things we can teach our kids is self-responsibility and that actions have consequences.

B．communication

D．responsibility

A．looking for

C．waiting for

C．disappointed

A．if　　　

B．disappointment

C．unacceptable

D．unbelievable

问答题

运用经济常识的有关知识，说明建设政治文明的必要性。