问题 计算题

造纸厂会产生含氢氧化钠的废水,需经处理呈中性后排放。为测定此废水中氢氧化钠的质量分数,工作人员取了40g废水样品加入到锥形瓶中,逐滴加入10%的稀硫酸,至恰好完全反应时,消耗稀硫酸49 g。计算废水中氢氧化钠的质量分数。

答案

n(H2SO4 )=49×10%g/98g/mol=0.05mol 。

设氢氧化钠物质的量xmol

H2SO4 + 2NaOH = Na2SO4 + 2H2O

1               2

0.05           x

1/2  = 0.05/x

x =0.1mol       

氢氧化钠的质量分数=×100%=10%

题目分析:依据题意可知,发生的反应是H2SO4 + 2NaOH = Na2SO4 + 2H2O,已知硫酸的质量为n(H2SO4 )=49×10%g/98g/mol=0.05mol,待求的是氢氧化钠的量,可根据方程式列出已知和未知的比例式求出,然后求出氢氧化钠的质量,再依据溶质质量分数的计算公式即可求解.

单项选择题

The General Electric Company, often criticized for the complexity of its structure and the resulting opacity of its numbers, said yesterday that it would break GE Capital, by far its largest business, into four businesses. The reorganization effectively eliminates the job of Denis J. Nayden, 48, the chairman of GE Capital. Each of the new units will have its own chief, who Will report directly to Jeffrey R. Immelt, G. E.’s chairman. "The reason for doing this is simple. I want more direct contact with the financial services teams," Mr. Immelt said.
The new businesses are GE Commercial Finance, GE Insurance, SE Consumer Finance and GE Equipment Management. Some support functions within GE Capital, including risk management and treasury, will now report to Dennis Dammerman, 57, a G. E. vice chairman who preceded Mr. Nayden as GE Capital’s chlef. Mr, Nayden will remain at G. E. as an adviser for now, but is expected to leave shortly to start a financial services firm.
Mr. Dammerman insisted that the reorganization had nothing to do with the increasing clamor from investors, regulators and the news media for greater transparency in accounting and for chief executives to take more responsibility for businesses: Analysts seem to believe him. "This is just what it appears to be, a managerial, reorganization which gives leaders more direct access to the office of the chairman," said Martin A. Sankey, a G. E. analyst.
The executives leading the new units will also sit on G.. E. ’s corporate executive council, a committee made up of the company’s top 25 executives, which meets periodically and discusses various strategic and management issues.
GE Capital, the company’s largest nit, provided $55 billion of G. E. ’s $124 billion in revenue last year and $ 5.6 billion of its $19.7 billion in pretax profits. The rest of G. E. had been divided into 11 other businesses, many of them--lighting and appliances are examples-much smaller than the new GE Capital units, yet each run by someone who reports directly to the chairman. Mr. Dammermn said that Mr. Immelt began talking about breaking GE Capital into more manageable pieces as soon as he took over as chief executive last September. "Jeff didn’t like the extra layer between him and the GE Capital businesses,"
G. E. has tried to make GE Capital less mysterious to ’the outside world. Although GE Capital was officially one unit, it had begun to report quarterly results in live product-related segments--a number that will be reduced to four with the new organization. And analysts say GE Capital’s management has been more accessible than it was in past years, and that Mr. Immelt and other G. E. corporate executives have been willing to discuss GE Capital in more depth.

The reorganization will enable GE’s chief executive to ______.

A.quiet down the unrest in the world

B.work in a more friendly business environment

C.have more direct contact with GE’s financial services teams

D.appear less mysterious to the outside world

单项选择题