题目

A farmer had some puppies（小狗）to   36   . He painted a sign advertising the puppies and   37__  nailing （钉）it to a post on the edge of his yard. As he was driving the last nail into the post, a little boy came to him.“Mister,” he said, “I want to buy one of your puppies.” “Well,” said the farmer, as he   38   the sweat off his face, “these puppies come from fine parents and cost   39   money. Do you have enough money?” The boy    40    his head for a moment. Then reaching into his pocket, he pulled out a handful of   41   and held it up to 如图所示，三名由不同金属材料制成的“士兵”，要游过以下两片海域，完成获是银矿的任务。(1)最先牺牲的“士兵”是_______兵，用化学方程式解释：________________(2)有一片“海域”最终会变成浅绿色，使它变色的“士兵”是________兵。(3)最终只有一名“士兵”完成任务，它是________兵。 Mg Mg +H2SO4===== MgSO4 +H2↑ Fe Cu 【解析】本题考查了金属的化学性质。 （1）根据金属活动性顺序可知，铁、铜、镁中铁、镁排在氢的前面，铜排在氢的后面，且三者中镁最活泼，镁兵最先牺牲；镁和硫酸反应生成硫酸镁和氢气，化学方程式是Mg +H2SO4== MgSO4 +H2↑； （2）铁能与硫酸反应生成浅绿色的氯化亚铁和氢气，铁与硝酸银反应生成浅绿色的硝...