取0.5摩尔每升某金属离子Mn+的溶液8ml恰好将0.2摩尔每升的某碳酸盐溶液30ml的CO32-全部沉淀.则n的值为

n(Mn+)=0.5*0.008=0.004mol
n(CO32-)=0.03*0.2=0.006MOL
2(Mn+)+n(CO32-)=M2(CO3)n
2 n
0.004 0.006
n=3