问题 阅读理解

阅读理解。

     Students learn many subjects at school, like Chinese, English, math and physics. Some students think it’s hard to do well in math. They say it’s boring. Why do they say this? First, some math problems are so hard for them. They spend a lot of time on them, but they can’t work them out, so they lost heart(失去信心). Second, they are afraid( 害怕) to ask their teachers for help. They think the teachers will laugh at them. Third, they think math class is very tiring because they need to use their brain(大脑)to find out the answers all the time.

     How can you do well in math? Here is some advice from a math teacher:

     1. Listen to the teacher carefully in class and do some extra(额外的) exercises after class.

     2. Ask the teacher for help if you don’t understand anything. Don’t be afraid.

     3. Don’t forget to go over (复习) your old lessons.

     If you do these things, you will find it much easier to do better in math.

1. Doing ________ math problem can make students lose heart.  

A. easy

B. difficult  

C. many

D. few

2. The advice is from ________.  

A. a math teacher

B. an English teacher

C. a student

D. a doctor

3. Some students think math class is very tiring because ________  

A. they have to listen to the teacher. 

B. they have to look after themselves. 

C. they need to use their brain to find out the answers all the time.

D. they need to help their classmates.

4. If you want to do better in math, you should NOT________.   

A. listen to the teachers carefully

B. ask the teacher for help 

C. go over your old lessons

D. lose interest in studying math

答案

1-4 BACD

填空题

四氯化钛(TiCl4)是制取航天航空工业材料——钛合金的重要原料。由钛铁矿(主要成分是FeTiO3)制备TiCl4等产品的一种工艺流程示意如下:

回答下列问题:

(1)往①中加入铁屑至浸出液显紫色,此时溶液仍呈强酸性。该过程中有如下反应发生:

2Fe3+Fe=3Fe2

2TiO2(无色)+Fe+4H=2Ti3(紫色)+Fe2+2H2O

Ti3(紫色)+Fe3+H2O=TiO2(无色)+Fe2+2H

加入铁屑的作用是                               

(2)在②→③工艺过程中需要控制条件以形成TiO2·nH2O溶胶,该溶胶的分散质颗粒直径大小在       范围。

(3)若把③中制得的固体TiO2·nH2O用酸清洗除去其中的Fe(OH)3杂质,还可制得钛白粉。已知25 ℃时,Ksp[Fe(OH)3]=2.79×10-39,该温度下反应Fe(OH)3+3HFe3+3H2O的平衡常数K=       

(4)已知:TiO2(s)+2Cl2(g)=TiCl4(l)+O2(g)  ΔH=+140 kJ·mol-1

2C(s)+O2(g)=2CO(g) ΔH=-221 kJ·mol-1

写出④中TiO2和焦炭、氯气反应生成液态TiCl4和CO气体的热化学方程式:                               

(5)上述工艺具有成本低、可用低品位矿物为原料等优点。依据绿色化学理念,该工艺流程中存在的不足之处是       (只要求写出一项)。

(6)依据下表信息,要精制含少量SiCl4杂质的TiCl4,可采用       方法。

 TiCl4SiCl4
熔点/℃-25.0-68.8
沸点/℃136.457.6
 

单项选择题