问题 问答题

双氧水(H2O2)是常用的消毒剂,也常用于实验室制氧气.

请回答:

(1)双氧水的相对分子质量为______;

(2)双氧水中氢、氧元素的质量比为______;

(3)双氧水中氧元素的质量分数为______.

答案

(1)根据相对分子的质量为组成分子的各原子的相对原子质量之和,可得双氧水的相对分子质量为:1×2+16×2=34;故答案为:34;

(2)根据化合物中各元素质量比=各元素的相对原子质量×原子个数之比,可得双氧水中氢、氧元素的质量比为:(1×2):(16×2)=1:17;故答案为  1:17;

(3)根据物质中元素的质量分数=

该元素相对原子质量×原子个数
该物质相对分子质量
×100%,可得双氧水中氧元素的质量分数为:
16×2
34
×100%=94.1%;故答案为:94.1%.

阅读理解

Every day in China, about 200 million children go to school. Many of them take school buses. What should we do to keep these students safe on the road?

On April 5, 2012,the State Council(国务院) published new rules about school bus safety. These new rules are stricter than the old ones.

Under the new rules, local governments must make sure that students go to nearby school or boarding schools to reduce traffic risks . Also, local governments must help kids in the countryside reach their school buses.

From now on, school buses have a speed limit of 80 km/h on highways and 60 km/h on normal roads. While on the road, other cars must let school buses go first.

The new rules also say that school buses must never be overloaded (超载的).

There are many other rules as well. A school bus must have more than seven seats. On each bus, there must be at least one adult to keep an eye on the kids. Each school bus must have a fire extinguisher (灭火器), a first aid kit (急救箱) and a GPS.

A series of school bus accidents happened in China in 2011. To stop such accidents, the Central Government decided to strengthen (加强) the rules for school buses.

The most serious accident happened in Gansu in November,2011. When a nine-seat minibus crashed. There were more than 60 children inside, and 21 of them died.

I hope such terrible things won’t happen again and all of us can pay more attention to the safety of the students.

小题1:What did the State Council publish on April 5, 2012?

A.New rules about school bus safety.

B.New rules about student safety.

C.New rules about student home.

D.New rules about class.小题2:According to the passage, the government made new rules because       .

A.21 students died in school bus accidents in 2011

B.School buses in China were not safe enough before

C.200 million children in China go to school by bus every day

D.the government encourages all students to take school buses小题3:What does the underlined “”word mean?

A.国外的

B.国内的

C.寄宿的

D.较远的小题4:What is the best title of this passage?

A.The most serious accident happened in 2011 in Gansu.

B.A school bus must have more than seven seats.

C.Local governments must help kids.

D.Safety first on the school bus.

实验题