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Mg(OH)_2的溶解度和K_(sp)都小于MgCO_3的,在含相同浓度的OH~-和CO_3~(2-)的情况下,加入含有同浓度Mg~(2+)的溶液时,首先得到Mg(OH)_2沉淀是毫无疑问的,但对于Mg(HCO_3)_2溶液中加NaOH溶液,到底是哪种物质首先沉淀,其关键在于Mg(HCO_3)_2溶液体系中CO_3~(2-)和OH~-浓度的实际大小。通过精确计算Mg(HCO_3)_2溶液中加NaOH溶液后上述两种离子浓度的变化情况,以及对沉淀条件和转化关系进行分析,认为在Mg(HCO_3)_2溶液中滴加NaOH溶液后,首先得到的沉淀是MgCO_3沉淀或aMgCO_3·bMg(OH)_2·cH_2O。
Mg (OH) _2 and K_ (sp) were all less than that of MgCO_3. When the solution containing the same concentration of Mg ~ (2+) was added under the same concentration of OH ~ - and CO_3 ~ (2-) However, for the solution of Mg (HCO_3) _2 added with NaOH solution, which is the first precipitation of Mg (OH) _2, the key point is that the content of CO_3 ~ (2) -) and OH ~ - the actual size of the concentration. By accurately calculating the changes of the above two ion concentrations after adding NaOH solution to the solution of Mg (HCO 3) 2 and analyzing the relationship between the precipitation conditions and the conversion, it is considered that after NaOH solution is added dropwise to Mg (HCO 3) 2 solution, The precipitate is MgCO_3 precipitate or aMgCO_3 · bMg (OH) _2 · cH_2O.