问题 选择题

能正确表示下列化学反应的离子方程式的是

A.金属铝溶于盐酸中:Al+2H+=Al3+H2

B.碳酸钙溶于硝酸中:2H+CO32=CO2↑+H2O

C.硫酸氢钠溶液中加入碳酸氢钠溶液:H++HCO3=CO2↑+H2O

D.在澄清石灰水中通入过量的CO2:Ca2+2OH+CO2=CaCO3↓+H2O

答案

答案:C

题目分析:A中电子的得失不守恒,应该是2Al+6H+=2Al3+3H2↑,A不正确;碳酸钙是难溶性物质,应该用化学式表示,B不正确;D中CO2是过量的,应该生成碳酸氢钙,D不正确,答案选C。

点评:该题是高考中的高频题,属于中等难度的试题,试题侧重考查学生的能力,有助于培养学生的应试能力。该题需要明确判断离子方程式正确与否的方法一般,即(1)检查反应能否发生。(2)检查反应物、生成物是否正确。(3)检查各物质拆分是否正确。(4)检查是否符合守恒关系(如:质量守恒和电荷守恒等)。(5)检查是否符合原化学方程式。

单项选择题
阅读理解

Astronomers (天文学家) say they are on the point of finding planets like Earth orbiting other stars, which is a key step in determining if we are alone in the universe.

A top NASA official and other leading scientists say that within four or five years they should discover the first Earth-like planet where life could develop, or may have already. A planet close to the size of Earth could even be found sometime this year.

At the annual American Astronomical Society conference this week, each discovery involving  so-called “exoplanets” —those outside our solar system —pointed to the same conclusion:Quiet planets like Earth where life could develop probably are plentiful.

NASA’s Dew Kepler telescope and a lot of new research from the suddenly hot and competitive exoplanet field caused noticeable buzz at the meeting.Scientists are talking about being at “an incredible special place in history” and closer to answering the question. “Are we alone? For the first time, there’s an optimism that sometime in our lifetimes we’re going to get to the bottom of that,” said Simon Worden,an astronomer who heads NASA’s Ames Research Center. “If I were a betting man, which I am, I would bet we’re not alone.”

“These are big questions that reflect upon the meaning of the human race in the universe,” the director of the Vatican Observatory, the Rev. Jose Funes, said Wednesday in an interview at this week’s conference.

Worden told The Associated Press: “I would certainly expect in the next four or five years we’d have an Earth-sized planet in the habitable (可居住的) zone.”

What is very important in determining if we are alone in the universe?

A. Finding an Earth-like planet.       B. Orbiting other stars.

C. Developing new telescopes.      D. Finding more exoplanets.

What’s an exoplanet?

A. It’s a planet like Earth.        B. It’s a planet outside our solar system.

C. It’s a planet orbiting the sun.   D. It’s a planet where life have developed.

The underlined phrase “get to the bottom of” probably means “__________”.

A. understand fully    B. make full use of

C. search for         D. do more research on   

From the passage we can learn that __________.

A. an Earth-like planet has been found

B. it’s been proved we are not alone in the universe

C. Jose Funes has found the meaning of the human race in the universe

D. the discovery of an Earth-like planet could happen in the near future