问题 填空题

含有少量二价锰盐的溶液,在浓HNO3中与PbO2混合煮沸,溶液呈现紫红色,PbO2转化为Pb(NO32,反应中无气体生成,该反应的离子方程式______,每消耗1mol氧化剂,被氧化的还原剂的物质的量为______mol.

答案

.根据题意知,在反应中PbO2得电子转化为为Pb(NO32,所以二氧化铅是氧化剂,则二价锰失电子作还原剂,溶液呈红色,说明二价锰离子被氧化生成高锰酸根离子,所以反应的离子方程式为 2Mn2++4H++5PbO2=5Pb2++2MnO4-+2H2O;

设每消耗1mol氧化剂,被氧化的还原剂的物质的量是x.

2Mn2++4H++5PbO2=5Pb2++2MnO4-+2H2O

2mol     5mol

x        1mol

x=0.4mol.

故答案为:2Mn2++4H++5PbO2=5Pb2++2MnO4-+2H2O;0.4mol.

阅读理解

Few Americans remain in one position or one place for a lifetime. They move from town to city to suburb, from high school to college in a different state, from a job in one region to a better job elsewhere, from the home where they raise their children to the home where they plan to live in retirement (退休). With each move they are forever making new friends, who become part of their new life at that time.

For many of them summer is a special time for forming new friendships. Today millions of Americans vacation abroad, and they go not only to see new sights but also with the hope of meeting new people. No one really expects a vacation trip to produce a close friend, but the beginning of a friendship is possible.

The word “friend ” can be applied to a wide range of relationships ---- to someone one has known for a few weeks in a new place, to a fellow worker, to a childhood playmate, to a man or woman, to a trusted confidant (知己).

小题1:. Many Americans move from place to place for the following reasons except           .

A.going to college

B.getting a better job

C.finding a place to live in retirement

D.saving money小题2:. Summer is a special time when many Americans           .

A.enjoy the sunlight

B.feel strange

C.travel to other countries

D.get a new job小题3: When summer comes, many Americans             .

A.hope to meet new people

B.expect to find some close friends

C.want to begin lasting friendships with new people

D.Both A and B小题4: From the passage it can be seen that a “friend” can be             .

A.a fellow worker

B.a football teammate

C.a boy or a girl

D.all of the above小题5:. Which of the following is the topic sentence of Paragraph 2?

A.For many of us summer is a special time for forming new friendships.

B.Today millions of Americans vacation abroad.

C.No one really expects a vacation trip to produce a close friendship.

D.But surely the beginning of friendship is possible.

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