问题 问答题

配平下列化学方程式:

(1)□KClO3

催化剂
.
□KCL+□O2

(2)□Al(OH)3+□H2SO4═□Al2(SO4)3+□H2O.

答案

(1)根据反应前后氧原子数目不变,反应前为3个氧原子,反应后为2个氧原子,最小公倍数为6,故KClO3前系数为2,O2前系数为3,再通过观察确定KCl前系数为3;

(2)复分解反应中,反应物两两交换成分,假设Al2(SO43前系数为1,则Al(OH)3前系数为2,H2SO4前系数为3,进而可推出H2O前系数为6.

故答案为:

(1)2KClO3

催化剂
.
2KCl+3O2↑;

(2)2Al(OH)3+3H2SO4═1Al2(SO43+6H2O.

阅读理解

Eleven-year-old Evan Green doesn’t want to save just one tree-he wants to save a whole rainforest!

In the Redwood City, Calif., a boy started a group called the Red Dragon Conservation Team four years ago to do just that. So far, the team’s members have raised $4,500. That’s enough to purchase and protect more than 16 acres of rainforest in Costa Rica through the Center for Ecosystem survival.

Every year, thousands of square miles of rainforest are destroyed worldwide. Logging(伐木)and farming are mostly likely to blame, scientists say. The loss is terrible news for animals and people. Even though rainforests cover less than 2 percent of the earth, they are home to half the world’s plants and animals. Rainforests also provide water and help control the earth’s climate.

Evan’s work to save the rainforests recently earned him a Barron prize for Young Heroes. The prizes are given to children or teenagers who have made a positive difference in the world. Evan’s goal is “to save enough rainforests to last forever”. He won’t have to do it alone. His actions have already inspired other kids to chip in. One girl asked for donations instead of presents on her birthday. She raised $850. Other kids are starting their own conservation teams.

Evan says everyone can help the planet-even by taking small steps such as recycling. He and his family try to make a difference every day. “We recycle, we try to limit our garbage… we’ve been walking a little more, and we buy local food,” Evan said.

48. How much does it cost to buy and protect an acre of rainforest in Costa Rica?

A. About $4,500.      B. About $850.     C. About $280.     D. About $1,000.

49. The underlined phrase “chip in” in Paragraph 4 probably means “________”.

A. look at                                    B. contribute money

C. ask for birthday presents               D. donate gifts

50. What Evan said in the last paragraph suggests that _________.

A. we can all do something to protect the earth

B. actions speak louder than words

C. we should learn to recycle from now on

51. What would be the best title for the passage?

A. Evan Green-a famous teenager    B. The Red Dragon Conservation Team

C. Rainforests are being destroyed    D. Boy gathers support for rainforests 

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