问题 选择题

用石墨作电极,电解1mol/L下列物质的溶液,溶液的pH值保持不变的是(  )

A.HCl

B.NaOH

C.K2SO4

D.NaCl

答案

A、电解盐酸,溶液中氢离子、氯离子放电,所以溶液中氢离子浓度逐渐减小,pH值逐渐变大,故A错误.

B、电解氢氧化钠,溶液中氢离子、氢氧根离子放电,相当于电解水,导致溶液中氢氧化钠的浓度增大,溶液的pH值增大,故B错误.

C、电解硫酸钾溶液,溶液中氢离子、氢氧根离子放电,相当于电解水,导致溶液中硫酸钾的浓度增大,但溶液中氢离子和氢氧根离子的浓度不变,所以溶液的pH值保持不变,故C正确.

D、电解氯化钠,溶液中氢离子和氯离子放电,所以溶液中氢离子浓度逐渐减小,pH值逐渐变大,故D错误.

故选C.

阅读理解

I once heard someone say, “We don’t remember days; we remember moments.” However, in today’s busy life we often forget to enjoy small pleasures while we make big plans.

In the race to be better or best, we sometimes lose sight of “just being”. And just being and enjoying a beautiful moment can provide some of life’s greatest pleasures. A fire on a cold winter night, a good book, an impressive sunset, a great meal, or a timeless moment with your child or a friend ... these moments, if we stop long enough to enjoy, are the essence (本质) of life.

I love to fish, especially for large-mouth bass (鲈鱼). About three years ago I was watching television late at night and got this crazy idea to go fishing in the lake behind my house. Of course, my wife thought I was nuts. It was almost midnight! I told her I was fine and took off.

I walked out to a warm summer breeze and looked up at the starry sky and breathtaking full moon. I allowed my senses to soak (浸泡) in every second — the sweet smell of flowers, the sound of every cricket (蟋蟀), the moon’s reflection dancing off the water — it was a perfect night.

After walking across a small field, I took out a flashlight, and selected a lure (饵). On my first cast I got a bass weighing over five pounds, one of the largest I had ever caught. I gently put it back into the water and continued my midnight adventure. During the next two hours I caught seventeen bass, all between two and five pounds. Although I’ve fished for almost fifty years, no fishing memory can top that night.

But that night provided far more than a fishing memory. It was a life memory. It provided me a picture of what life could be like if I just slowed down enough to enjoy the moments. On my way back to the house, as I walked through the tall grass, I took one last look at the sky and stopped to say, “Thank you, God, for giving me this night.”

64. The purpose of the passage is to ______.

A. suggest people should make big plans                          

B. tell people to do what they like

C. advise people to enjoy beautiful moments

D. encourage people to follow their dreams

65. What does the underlined word “nuts” in Paragraph 3 mean?

A. Determined.               B. Ill.      C. Tired.                 D. Crazy.

66. The fourth paragraph is mainly about ______.

A. the description of the night

B. the author’s fishing experience

C. the author’s attitude towards life

D. what the author did that night

67. We can learn from the passage that night the author ______.

A. caught fewer fish than before

B. enjoyed real small pleasures

C. went to bed around 1:00 am

D. went fishing with his wife

问答题 简答题