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(12分)某同学为了探究锌与硫酸反应过程中的速率变化,他在100mL稀硫酸中加入足量的锌粉,标用排水集气法收集反应放出的氢气,实验记录如下(累计值): 时间(min) 1 2 3 4 5 氢气体积(mL)(标准状况) 50 120 232 290 310 (1)哪一时间段(指0~1、1~2、2~3、3~4、4~5min)反应速率最大______________,原因是______________________________________________。 (2)哪一时间段的反应速率最小________________,原因是___________________。 (3)求2~3分钟时间段以硫酸的浓度变化来表示的该反应速率(设溶液体积不变,要写出计算过程)______________________________________________________。 (4)该同学在用稀硫酸与锌制取氢气的实验中,发现加入少量硫酸铜溶液可加快氢气的生成速率。请回答下列问题: ①上述实验中涉及到的离子反应方程式有 ; ②硫酸铜溶液可以加快氢气生成速率的原因是 ; ③实验室中现有Na 2 SO 4 、MgSO 4 、Ag 2 SO 4 、K 2 SO 4 等4种溶液,可与实验中CuSO 4 溶液起相似作用的是 ; ④该同学通过实验进一步研究了硫酸铜的量对氢气生成速率的影响。该同学最后得出的结论为:当加入少量CuSO 4 溶液时,生成氢气的速率会大大提高。但当加入的CuSO 4 溶液超过一定量时,生成氢气的速率反而会下降。请分析氢气生成速率下降的主要原因 。
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