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【题目】已知硅能与碱反应生成氢气,将镁、铝、硅的混合物分为等质量的两份,一份跟足量的NaOH溶液反应,另一份跟足量的盐酸反应,最终产生的H2一样多,则镁与硅的物质的量之比为多少?

【答案】2∶1

【解析】Mg不和NaOH反应,所以

2Al+2NaOH+2H2O===2NaAlO2+3H2↑,

Si+2NaOH+H2O===Na2SiO3+2H2

Si不和HCl反应,所以

2Al+6HCl===2AlCl3+3H2↑,

Mg+2HCl===MgCl2+H2↑。

因为产生的H2一样多,等量的Al分别产生的H2是1∶1,

所以Si和Mg产生的氢气就该是1∶1,

所以由方程式得n(Mg)∶n(Si)=2∶1。

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