问题 填空题

某溶液中可能含有Na+、K+、Mg2+、I、SO32、SO42等离子中的全部或其中的几种。现分别进行以下实验操作:

①用洁净的铂丝蘸取溶液在无色火焰上灼烧,焰色呈黄色;②取原溶液,滴加少量溴水,振荡后溶液仍为无色。③取原溶液,加入盐酸酸化的Ba(NO3)2溶液后,产生白色沉淀。

(1)原溶液中一定存在的离子是     ,一定不存在的离子是          

(2)上述①~③,的操作中,   是错误的,应改为       ,以便确定       离子的存在。

(3)为确定             离子是否存在,应补充的实验是①                            

                                                                         

答案

(1)Na+、SO32- ;Mg2+  .

(2) ③;先加盐酸酸化后,再加BaCl2溶液;SO42-

(3)I-、K+;透过蓝色钴玻璃观察火焰,焰色呈紫色的则含有K+,否则没有K+

取原溶液少许加入试管,滴入用HNO3酸化的AgNO3溶液,若产生黄色沉淀,则有I-,否则没有I-

关键要从②中信息得出一定有SO32,一定没有Mg2+,而I不能确定,还要注意③中加入的是Ba(NO3)2,在酸性条件下,能将SO32氧化成SO42对检验造成干扰。

单项选择题 B型题
阅读理解

阅读理解。

     When Babbage was working at Cambridge, a new idea occurred to him. He wanted to construct a

calculating machine to work out the solutions (解法) to maths problems not only with correctness but

also with a speed beyond the power of any human mind. His machine could solve problems involving

(涉及) long rows of figures in one continuous operation (运算).

     In 1822 Babbage exhibited his invention and won a prize from the government. After that, he

immediately started to work on a larger machine designed to solve more difficult problems. Although he

received some money left by his father, the money was not enough to support his design. He wrote to

the government about his plan and was given £2500 to start with, a sum worth much more in those days

than it is now.

     Babbage continued his work in London for four years. Then his health broke down, and he had to take

a long holiday abroad. When he returned to London in 1828, he was at the end of his resources. Many bills

remained unpaid. His chief assistant and co-workers quarreled with him and left with many expensive tools.

For one year no work was done. During this period, Babbage, whose mind was always active, suddenly

thought of a completely new idea for the machine. He rushed to meet the government officials to explain his

new idea. But this time, they were unwilling to help him. For eight years, they refused to say whether they

wanted the machine or not, and their final answer was "No." 

     From 1828 to 1839, Babbage held the position of professor at Cambridge very successfully. But his

greatest work was the unfinished calculating machine which stood covered in dust in his house. It was the

beginning of the modern computer.

1. The machine Babbage designed would solve difficult maths problems ______.

A. in one operation with few mistakes

B. in more than one operation without any mistakes

C. in more than one operation with slight mistakes

D. in one operation without any mistakes

2. Babbage failed to continue his research work in 1828 mainly because _______.

A. he was in poor health

B. he almost ran out of money

C. his co-workers argued with him

D. he spent all his money on his bills

3. Babage explained his new idea to the government officials, expecting that _______.

A. they would agree to his plan

B. they would pay for his new idea

C. they would support him with money

D. they would exhibit his new design

4. From the passage, we can infer that _______.

A. Babbage failed to be a famous scientist at Cambridge

B. Babbage always had new ideas but gave them up easily

C. Babbage always needed support from the government officials

D. Babbage was the first designer of the modern computer