问题 实验题

(9分)某学生用0.2000mol·L-1的标准NaOH溶液滴定未知浓度的盐酸,其操作步骤如下:

①量取20.00mL待测液注入洁净的锥形瓶中,并加入3滴酚酞溶液。

②用标准液滴定至终点,记录滴定管液面读数,所得数据如下表:

滴定次数盐酸体积NaOH溶液体积读数(mL)
滴定前滴定后
120.000.0018.10
220.000.0016.30
320.000.0016.22
请回答下列问题:

(1)步骤①中,量取20.00mL待测液应使用________________(填仪器名称),若在锥形瓶装液前残留少量蒸馏水,将使测定结果_______________(填“偏大”、“偏小”或“无影响”)。

(2)步骤②中,滴定时眼睛应注视________________(填仪器名称),判断到达滴定终点的依据是___________________________________________。

(3)第一次滴定记录的NaOH溶液的体积明显多于后两次的体积,其可能的原因是_______________________(填字母)

A.滴定前滴定管尖嘴有气泡,滴定结束时无气泡

B.锥形瓶装液前用待测液润洗

C.NaOH标准液保存时间过长,有部分Na2CO3生成

D.滴定终点时,俯视读数

(4)根据上表记录数据,通过计算可得该盐酸的浓度为______  mol·L-1 

答案

(9分)

(1)酸式滴定管(1分);无影响(1分)

(2)锥形瓶(1分)锥形瓶中溶液由无色变为浅红色,且半分钟内不变色(2分)

(3)AB(2分)

(4)0.1626(2分)

阅读理解

Many skilled young people are being forced into part-time and unskilled work, the report says. It warns of a "crisis" with more than six million people so disillusioned they have given up looking for work. The ILO(International Labor Organization)wants governments to make job creation a priority. It wants more training schemes, and also tax breaks for employers.

"The youth unemployment crisis can be beaten but only if job creation for young people becomes a key priority in policymaking and private sector investment picks up significantly," said Jose Manuel Salazar-Xirinachs, executive director of the ILO's employment sector.

Since 2007, the number of young people without jobs has risen by four million - up from less than 12%, the Global Employment Trends for Youth Report says. Almost 13% of people aged between 15 and 24 - or almost 75 million - have no work, although this is slightly down on its peak in 2009.

In the European Union, one in five young people are looking for work, the report claims. Some 27.9% of youths were unemployed in North Africa last year —a rise of five percentage points on 2010. In the Middle East, the figure stood at 26.5% in the report's regional breakdown. Even in East Asia, perhaps the most economically active region, the unemployment rate was 2.8 times higher for young people than for adults, the report said.

But, the ILO report reveals, the true picture of youth unemployment is even more pessimistic. Many young people are extending their time in higher education because they cannot find jobs. Others are taking part-time unskilled work because they cannot find work in the fields they trained for.

The ILO says that more than six million young people worldwide have given up looking for work and are becomingly increasingly detached from society. By not using their skills they are losing them, the report says, and if there is no improvement in the jobs market soon, they may be not only unemployed, but unemployable.

The ILO suggests offering tax breaks to businesses hiring young people and offering more programmes to help kick-start careers.

小题1:Which of the following is true according to Jose Manuel Salazar-Xirinachs?

A.Since 2007, the number of young people out of job has risen to 4 million.

B.Nearly 13% of the young people have no work.

C.Job creation should be made a key priority in policymaking.

D.The youth unemployment rate can never go down.小题2:The various figures in paragraph 3 and 4 were used to show_______.

A.The employment situation is serious only in the European Union

B.The global youth employment situation is depressing

C.East Asia enjoys a high youth employment rate

D.Compared with the situation in 2009, the youth employment in 2007 is slightly better小题3:According to ILO, the following are caused by high youth unemployment rate except_______.

A.The government calls on young people to take up whatever job is available

B.Many young people are making their time in higher education longer

C.Some young people are taking part-time unskilled work

D.Many young people have given up looking for work小题4:The ILO offered many solutions to the crisis of youth unemployment, including_______.

a. making job creations a priority          b. more training schemes      

c. encouraging public investment           d. tax breaks for employers     

e. offering more entrepreneurship programmes to help start careers

A.a b c e

B.b c d e

C.a c d e

D.a b d e

判断题