问题 选择题

关于酸和碱的描述正确的是(  )

A.紫色石蕊试液遇碱溶液变蓝色

B.生石灰和熟石灰都属于碱

C.酸就是有酸味的物质

D.碱就是有腐蚀性的物质

答案

A、紫色的石蕊试液遇碱性溶液变蓝色,碱的溶液显碱性,所以紫色石蕊试液遇碱溶液变蓝色.

B、碱是电离时生成的阴离子全部是氢氧根离子的化合物,所以碱中一定含有氢氧根,而生石灰不含氢氧根,所以不是碱是氧化物,熟石灰是氢氧化钙是碱,故错误.

C、酸是电离时生成的阳离子全部是氢离子的化合物,有酸味不一定是酸,故错误.

D、碱是电离时生成的阴离子全部是氢氧根离子的化合物,有腐蚀性不一定是碱,如浓硫酸有腐蚀性是酸不是碱,故错误.

故选A

阅读理解

阅读理解

     In every country, there are thousands of people who want to help out. Many join organizations

run(管理) by their governments, for example, the Peace Corps in the United States and Voluntary

Service Overseas in Britain. Since the powerful(猛烈的) earthquake took place in Sichuan, more

than 200 thousand volunteers across China have been helping there! They do all kinds of work or

come up with ways to help improve life. Some offer their professional skills for free. Others have

no qualifications(资历), but they love to work hard to help.

     One of the most famous volunteers in the world was Mother Teresa. She could be the best

volunteer because she gave her life to helping the poorest people of Calcutta. She helped the

homeless, cared for the sick, gave out food, and became the mother of those without families.

     Now more and more teenagers actively look for volunteering opportunities, too. They volunteer

because they think it will be fun or they will learn something. They also like the idea of being helpful

to others, even if it is just handing out books for the teacher. As they get older, these reasons are still

the same, but there are other important reasons for volunteering such as learning on-the-job, getting

work experience, and improving their social life.

     All volunteers bring joy to the people they help in so many ways. They might read books to the

blind, fix up broken homes, find ways to get water for villages, Could you be a volunteer? What kind

of volunteer work could you do? There is someone in the world who needs you.

1. The Peace Corps is __________ in the United States.

A. a city

B. an organization

C. a volunteer

D. a school

2. The underlined word "those" in the passage means "__________".

A. the homeless

B. the sick

C. the poor

D. the kids

3. What is NOT the reason for teenagers to be volunteers according to the passage?

A. They want to make more friends.

B. They want to be helpful.

C. It helps them get work experience.

D. It can improve their social life.

4. Which of the following is true according to the passage?

A. Volunteers need qualifications.

B. Volunteers offer their help without any pay.

C. Young kids can't be volunteers.

D. Some volunteers bring joy to others.

5. What is the main idea of this passage?

A. The world needs volunteers.

B. Mother Teresa was a great volunteer.

C. Volunteers do all kinds of work.

D. There are different ways of volunteering.

问答题 简答题