问题 计算题

实验室有一瓶未知浓度的BaCl2溶液,某同学取出150g该溶液于烧杯中,向其中逐滴加入溶质质量分数为26.5%的Na2CO3溶液。反应过程中生成沉淀的质量与所用Na2CO3溶液质量的关系如下图所示。已知:BaCl2+Na2CO3=BaCO3↓+2NaCl

请计算:

(1)配制26.5%的Na2CO3溶液80g,需要Na2CO3固体_______g。

(2)BaCl2溶液的溶质质量分数是多少?(写出计算过程,结果保留到0.1%)

答案

(1)21.2g

(2)解:从图甲中获知,当BaCl2完全转化为沉淀时消耗Na2CO3溶液的质量为40g。设BaCl2的质量为x,则

BaCl2+Na2CO3=BaCO3↓+2NaCl

208  106

x  40g×26.5%

;解得:x=20.8g

该BaCl2溶液的溶质质量分数=(20.8g/150g)×100%=13.9%

答:该BaCl2溶液的溶质质量分数为13.9%。

阅读理解

     Let’s say you took violin lessons all through primary school, but you haven’t got the instrument out of its case in years. Were all those lessons a waste of your parents’ money because you didn’t become a great violinist?

     Not at all. Even though it has been a long time since you played the violin, a new study shows that as little as one year of music training can have a positive influence (影响) on your brain that will last the rest of your life.

     In an experiment comparing (比较)children who had taken music lessons to those who hadn’t, Lanrel Tiniest, a researcher of the Institute for Music and the Mind at Ontario’s MeMaster University, diseoveted that the musically trained kids had larger brain responses (反应)to the sound recognition (分辨)exams. Traitor’s findings tell the possibility that musical training can actually change the brain’s bearing cortex (皮层), leading to better overall learning skills.

     The study’s results point out that “musical training(but not necessarily passive (被动)listening to music)influences attention and memory, which makes a possibility that musical training might lead to better learning across a number of fields.” Trainer said in a report.

     The effects (效果)of music training are even more easily seen in children with difficulties on language. “A music training that can strengthen the hearing skills of children who have difficulty in reading may also help improve some of their language abilities,” said Gottfried Schlang, who has also studied music training and learning.

     So, whether or not you can play a Tchaikovsky symphony part, it’s likely that your years of music lessons prepared your brain for all the speeches, emails, and conversations that are part of your life today. To help make sure that kids today have the same chances for music inspired (激发)brain development, help out by volunteering with or giving away instruments to your school’s music training department.

1. Which of the following statements is TRUE?    

A. Parents think that musical lessons are a waste of money.

B. One year of music training can also have a helpful influence.

C. Musical practice can make the brain become much heavier.

D. Most children spend much time learning to play an instrument.

2. The underlined word “strengthen” means         .

A. make stronger    

B. keep balance    

C. get achievement    

D. exchange something

3. Which of the following could be the best title of the text?   

A. How to Study Well with Music Training

B. Children Must Take Some Music Lessons

C. You Can Also Become a Great Musician

D. Music Training Can Build up Your Brain

4. What can we learn from the passage?  

A. Learning skills depend on music training greatly.

B. Children who have difficulties with language enjoy music.

C. The writer took violin lessons when he was young.

D. Music training can also help improve one’s language ability.

单项选择题