问题 问答题

市售双氧水溶液中含H2O2的质量分数为30%,密度1.1122g/cm3.分别计算(写出计算过程,结果精确到0.1):

(1)每1000mL上述双氧水溶液中,含H2O2多少克?

(2)已知H2O2在MnO2催化下,可发生下列反应:2H2O2

 MnO2 
.
 
2H2O+O2↑,欲用该溶液制取96g氧气,至少需取用30%的H2O2溶液多少毫升?

答案

(1)1000cm3=1000mL,1000cm3×1.1122g/cm3×30%=333.7g

(2)设至少需H2O2的质量为x

2H2O2

 MnO2 
.
 
2H2O+O2

68               32

x                96g

68
x
=
32
96g
  x=204g

需取用30%的H2O2溶液的体积为:204g÷30%÷1.1122g/cm3=611.4cm3

答:每1000mL双氧水溶液中含H2O2的质量为333.7g;至少需取用30%的H2O2溶液611.4mL.

阅读理解

Dukuly Dogbah, a 14-year-old Liberian(利比亚的) boy, grew up in a war. He was born in the same year the Liberian war started. Since then fighting between the government forces and the rebel armies has not stopped.

Dukuly is one of around 10,000 child soldiers in Liberia. At 10, Dukuly lost contact with his family in the war and had to fight for the rebels. During the war he learnt to kill people with guns. He has killed many people and seen many of his friends die. “You have to," he said, "because it is war."

Lots of children had to join the army. Some did it out of their own will. They thought they would be safe with a gun. The army leaders use child soldiers because they are easy to control and do not get paid much.

Child soldiers do terrible things. Most of them take drugs. “I cannot control myself because it makes me brave," Dukuly said.

There are 120,000 child soldiers in Africa and 300,000 around the world. Many child soldiers die and nobody cares for them. According to a United Nation's report, 23 armies in the world use children. Some African and Asian countries often use child soldiers. Myanmar(缅甸) has the highest number of child soldiers in their army:  around 50,000. Most of the child soldiers are under 18 years of age and the youngest is only 7 years old.

The UN has called for the protection of children in war. The UN Children's Fund wants African countries to ban(禁止) child soldiers. Many UN organizations are trying to take child soldiers away from war and send them back to school.

小题1:Dukuly was born when    .

A.the Liberian war started

B.his family were killed in the war

C.he lost touch with his family

D.the government armies caught him小题2:The following are the reasons for so many child soldiers EXCEPT_______.

A.they are easy to control

B.they don't get much paid

C.having a gun makes them feel safe

D.they like to do terrible things.小题3:There are        child soldiers all over the world.

A.120.000

B.300,000

C.420.000

D.50,000小题4:According to the last two paragraphs,we know that the UN       .

A.has calle for people to protect children in war

B.has banned African countries from having child soldiers

C.has sent those child soldiers back to school

D.has taken the child soldiers under 7 away from war

多项选择题