题干

MnO2是一种重要的无机功能材料,工业上从锰结核中制取纯净的MnO2工艺流程如图所示:

部分难溶的电解质溶度积常数(Ksp)如下表:

化合物

Zn(OH)2

Fe(OH)2

Fe(OH)3

Ksp近似值

10﹣17

10﹣17

10﹣39

已知:一定条件下,MnO4﹣可与Mn2+反应生成MnO2

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    The kids in a village in Ethiopia wear dirty, ragged clothes. They sleep beside cows and sheep in huts made of sticks and mud. They have no school. Yet they all can chant the English alphabet, and some can make words.

    The key to their success: 20 tablet computers(平板电脑) dropped off in their Ethiopian village in February by a U.S. group called One Laptop Per Child.

The goal is to find out whether kids using today's new technology can teach themselves to read in places where there are no schools or teachers. The Massachusetts Institute of Technology researchers analyzing the project data say they're already amazed. “What I think has already happened is that the kids have already learned more than they would have in one year of kindergarten,” said Matt Keller, who runs the Ethiopia program.

    The fastest learner—and the first to turn on one of the tablets—is 8-year-old Kelbesa Negusse. The device's camera was disabled to save memory, yet within weeks Kelbesa had figured out its workings and made the camera work. He called himself a lion, a marker of accomplishment in Ethiopia.

With his tablet, Kelbasa rearranged the letters HSROE into one of the many English animal names he knows. Then he spelled words on his own. “Seven months ago he didn't know any English. That's unbelievable,” said Keller.

    The project aims to get kids to a stage called “deep reading,” where they can read to learn. It won't be in Amharic, Ethiopia's first language, but in English, which is widely seen as the ticket to higher paying jobs.