问题 选择题

除去下列物质中的少量杂质(括号内是杂质),其中方法正确的是(  )

选项物质除去杂质的方法
ACu粉(Zn粉)加入过量稀盐酸,搅拌、过滤、洗涤、干燥
BCaO粉末(CaCO3粉末)加入过量水、搅拌、过滤、洗涤、干燥
CFeCl3溶液(CuCl2溶液)加入过量的锌粉,过滤
DNaCl溶液(Na2SO4溶液)加入过量BaCL2溶液,充分反应后过滤
 

答案

答案:A

题目分析:A、锌粉能与稀盐酸反应生成硫铜和水,铜不与稀盐酸反应,再过滤、洗涤、干燥,能除去杂质且没有引入新的杂质,符合除杂原则,故选项所采取的方法正确.B、CaO能与水反应生成氢氧化钙,碳酸钙难溶于水,反而会把原物质除去,不符合除杂原则,故选项所采取的方法错误.C、锌粉与氯化铜、氯化亚铁溶液均能发生反应,不但能把杂质除去,也会把原物质除去,不符合除杂原则,故选项所采取的方法错误.D、硫酸钠溶液能与过量的氯化钡溶液反应生成硫酸钡沉淀和氯化钠,能除去杂质但引入了新的杂质氯化钡,不符合除杂原则,故选项所采取的方法错误.

单项选择题

If you are a tourist interested in seeing a baseball game while in New York, you can Find out which of its teams are in town simply by sending a message to AskForCents. com. In a few minutes, the answer comes back, apparently supplied by a machine, but actually composed by a human. Using humans to process information in a machine-like way is not new- it was pioneered by the Mechanical Turk, a famed 18th-century chess-playing machine that was operated by a hidden chessmaster. But while computers have since surpassed the human brain at chess, many tasks still baffle even the most powerful electronic brain.

For instance, computers can find you a baseball schedule, but they cannot tell you directly if the Yankees are in town. Nor can they tell you whether sitting in the bleachers is a good idea on a first date. AskForCents can, because its answers come from people. "Whatever question you can come up with, there’s a person that can provide the answer-- you don’t have the inflexibility of an algorithm-driven system," says Jesse Heitler, who developed AskForCents. Mr. Heitler was able to do this thanks to a new software tool developed by Amazon, the online retailer, that allows computing tasks to be farmed out to people over the internet. Aptly enough, Amazon’s system is called Mechanical Turk.

Amazon’s Turk is part toolkit for software developers, and part online bazaar: anyone with internet access can register as a Turk user and start performing the Human Intelligence Tasks (HITs) listed on the Turk website (mturk.com ). Companies can become "requesters" by setting up a separate account, tied to a bank account that will pay out fees, and then posting their HITs. Most HITs pay between one cent and $ 5. So far, people from more than 100 countries have performed HITs, though only those with American bank accounts can receive money for their work; others are paid in Amazon gift certificates.

Mr. Heitler says he had previously tried to build a similar tool, but concluded that the infrastructure would be difficult to operate profitably. Amazon already has an extensive software infrastructure designed for linking buyers with sellers, however, and the Turk simply extends that existing model. Last November Amazon unveiled a prototype of the system, which it calls "artificial artificial intelligence". The premise is that humans are vastly superior to computers at tasks such as pattern recognition, says Peter Cohen, director of the project at Amazon, so why not let software take advantage of human strengths

Mr. Cohen credits Amazon’s boss, Jeff Bezos, with the concept for the Turk. Other people have had similar ideas. Eric Bonabeau of Icosystem, an American firm that builds software tools modeled on natural systems, has built what he calls the "Hunch Engine" to combine human intelligence with computer analysis. The French postal service, for example, has used it to help its workers choose the best delivery routes, and pharmaceutical researchers are using it to determine molecular structures by combining their gut instincts with known results stored in a database. And a firm called Seriosity hopes to tap the collective brainpower of the legions of obsessive players of multiplayer online games such as "World of Warcraft", by getting them to perform small real-world tasks (such as sorting photographs) while playing, and paying them in the game’s own currency.

The last sentence of the first paragraph means()

A. computers have never been superior to human intelligence

B. human intelligence can still outperform computers

C. computers will eventually baffle many tasks humans give them

D. human intelligence will fail in the face of electronic chessmasters

填空题