D 【试题分析】 解析:电解时,阳极上金属按还原性由强到弱的顺序(Zn>Fe>Ni>Cu>Pt)发生氧化反应,即ZnZn2++2e-、FeFe2++2e-、NiNi2++2e-;电解过程中,因为粗镍中含有少量Fe、Zn、Cu、Pt等杂质,因而当阳极溶解Zn、Fe、Ni而阴极析出Ni时,得失电子总数相等,则阳极减少的质量与阴极增加的质量不可能相等;电解后,溶液中存在的金属阳离子除Fe2+和Zn2+外,还可能存在Ni2+;因为Fe、Zn比Ni活泼,所以电解槽底部的阳极泥中不可能存在Fe、Zn,只存在Cu和Pt。故答案为D。
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