题目.(《中学化学教学参考》2014年1-2期72面“四、离子反应”第22题)某混合物的水溶液,可能含有以下离子中的若干种:K~+、Al~(3+)、Fe~(3+)、Mg~(2+)、Ba~(2+)、NH_4~+、Cl~-、CO_3~(2-)、SO_4~(2-)。现分别取100 mL的两等份溶液进行如下实验:①第一份加过量NaOH溶液后加热,收集到0.02 mol气体,无沉淀生成,同时得到溶液甲。②向甲溶液中通入过量CO_2,生成白色沉淀,沉淀经过滤、洗涤、灼烧后得到1.02 g固体。③第二份加足量BaCl_2溶液后,生成白色沉淀,沉淀经足 (“Secondary Chemistry Teaching Reference”, Vol. 1-2, No. 12, 2014, p.24). The aqueous solution of a mixture may contain several of the following ions: K ~ +, Al ~ ( Fe3 +, Mg2 +, Ba2 +, NH4 +, Cl ~ -, CO_3 ~ (2 -) and SO_4 ~ (2-). Now take two 100mL aliquots of the following experiments: ① After the first excess NaOH solution was heated to collect 0.02 mol of gas, no precipitate generated, while the solution A. ② A solution into the excess CO_2, resulting in a white precipitate, the precipitate was filtered, washed and dried to give 1.02 g of solid. ③ After the second addition of BaCl 2 solution, a white precipitate is formed and the precipitate is precipitated