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问题 填空题

现已研究出用铁粉（包裹在多孔泡沫塑料袋中）代替氧化钙做食品的干燥剂，请你写出用铁粉代替CaO粉末的优点是______．写出氧化钙吸水的化学方程式______．

答案

食品容易吸收空气中的水分变潮湿，并与空气中的氧气发生缓慢氧化而腐败，所加入的铁粉不但能吸水还能消耗氧气，减缓食品变质；氧化钙与水反应生成氢氧化钙，化学方程式为：CaO+H2O=Ca（OH）2．

故答案为：不但能吸水，使食品保持干燥；而且能吸收氧气，防止食品腐败．

CaO+H2O=Ca（OH）2

问答题

A、B、C、D、E五种物质都含1～18号元素中的某 一 元素，它们按图所示关系相互转化，已知A为单质．

（1）写出A→E的化学式：

A______   B______C______   D______E______

（2）写出A→D、C→D、反应的化学方程式：A→D______；C→D______．
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单项选择题

Drug use is rising dramatically among the nation’ s youth after a decade of decline. From 1993 to 1994, marijuana use among young people (1) from 12 to 17 jumped 50 percent. One in five high school seniors (2) marijuana daily. Monitoring the Future, which (3) student drug use annually, reports that negative attitudes about drugs have declined for the fourth year in a row. (4) young people see great risk in using drugs. Mood-altering pharmaceutical drugs are (5) new popularity among young people. Ritalin, (6) as a diet pill in the 1970s and now used to (7) hyperactive children, has become a (8) drug on college campuses. A central nervous system (9) , Ritalin can cause strokes, hypertension, and seizures. Rohypnol, produced in Europe as a (10) tranquilizer, lowers inhibitions and suppresses short-term memory, which has led to some women being raped by men they are going out with. (11) taken with alcohol, its effects are greatly (12) . Rock singer Kurt Cobain collapsed from an (13) of Rohypnol and champagne a month before he committed (14) in 1994. In Florida and Texas, Rohypnol has become widely abused among teens, who see the drug as a less expensive (15) for marijuana and LSD. Alcohol and tobacco use is increasing among teenagers, (16) younger adolescents. Each year, more than one million teens become regular smokers, (17) they cannot legally purchase tobacco. By 12th grade, one in three students smokes. In 1995, one in five 14-year-olds reported smoking regularly, a 33 percent jump (18) 1991. Drinking among 14-year-olds climbed 50 percent from 1992 to 1994,and all teens reported substantial increases in (19) drinking. In 1995, one in five 10th graders reported having been drunk in the past 30 days. Two-thirds of high school seniors say they know a (20) with a drinking problem.

18（）

A.in

B.to

C.since

D.for
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