问题 选择题

下列有关二氧化碳的检验、性质、制备和用途的实验能达到目的是(  )

A.将燃着的木条伸入集气瓶,火焰立即熄灭,证明瓶内原有气体就是二氧化碳

B.二氧化碳通入紫色石蕊试液中,溶液变蓝

C.用块状石灰石和稀硫酸迅速制备二氧化碳

D.干冰能用于人工降雨

答案

A、氮气和二氧化碳都不支持燃烧,将燃着的木条伸入集气瓶,火焰立即熄灭,该气体可能是二氧化碳,也可能是氮气,故A错误;

B、二氧化碳会与水生成碳酸,碳酸显酸性,会使紫色石蕊变红色,故B错误;

C、石灰石会与硫酸反应生成微溶于水的硫酸钙,阻碍反应的继续进行,故C错误;

D、干冰是固态二氧化碳,汽化会吸收热量水蒸气迅速冷凝成水滴,故D正确;

故选D.

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单项选择题

Compared with IBM, Microsoft is a mere young company. Founded in 1975, it rose swiftly to dominate the world of personal computing with its Windows operating system and Office suite of word-processing and other productivity tools. But the company is now showing some worrying signs of middle-age fatigue. In particular, it is struggling to find a growth strategy that will enthuse disappointed shareholders.

Complaint are understandable. Since Steve Ballmer took over from Bill Gates as chief executive in 2000, Microsoft’s share price has decreased and the company has lost its reputation as a tech trend-setter. It has been left behind in hot areas such as search and social networking by younger companies, some of which love to thumb their noses at their older rival. Eric Schmidt, the executive chairman of Google, recently proclaimed that leadership in the tech world had passed from Microsoft and others to a "Gang of Four" fast-growing, consumer-oriented businesses: Google, Apple, Amazon and Facebook.

Few would object to that. The question is: what,if anything, can Microsoft do to change it In at least some respects, the company appears to be suffering from similar ailments to those that laid IBM low before Lou Gerstner was hired in 1993 to get it back on its feet. These include arrogance bred of dominance of a particular area-mainframe computers at IBM, personal computers at Microsoft—and internal fiefs that hamper swift change.

As IBM’s experience shows, recovery in the tech world is possible. And some observers see encouraging signs of progress at Microsoft. Sarah Rotman Epps of Forrester, a research firm, reckons that Windows 8, a forthcoming version of Microsoft’s operating system, could be a serious competitor to Google’s Android on tablet computers if the company can get it to market next year.Microsoft is also in far better shape financially than IBM was at its lowest point, so it can afford to splash out on acquisitions such as its recent $8.5 billion purchase of Skype, an internet-phone and video-calling service.

That bet and an alliance with Nokia in mobile phones show that Microsoft is trying to bulk up in promising areas. Yet sceptics worry that such initiatives are not the product of an comprehensive strategic vision, but are instead temporary moves designed to calm critics who fear Microsoft is drifting downwards. David Einhorn, a prominent hedge-fund manager whose fund holds shares in Microsoft, has publicly called for a change at the top of the firm, arguing that Mr Ballmer is "stuck in the past". So far, the company’s board, chaired by Mr Gates, has backed its chief executive. But if IBM’s history is a guide, Microsoft may yet end up jettisoning its leader.

According to the text, which of the following is true of Microsoft()

A. It is considering hiring a new CEO

B. It is engaged in an internal reform

C. It can rival IBM in mainframe computers

D. It is committing the mistakes IBM once committed