题干

为探究一瓶久置的氢氧化钠溶液(原溶质质量分数16%)是否变质,同学们提出了多种方案,其中一种方案设计如下:

【查阅资料】:氢氧化钠溶液与空气接触可能发生的反应:

            2NaOH+CO2═Na2CO3+H2O

            Na2CO3+CO2+H2O═2NaHCO3

            NaOH与NaHCO3在溶液中发生反应:

            NaOH+NaHCO3═Na2CO3+H2O

【假设猜想】:1.该溶液未变质,溶质成分只有NaOH ;2.该溶液已变质

【实验探究】:向一定质量的洁净烧杯中加入m1g该氢氧化钠溶液,再加入溶质质量分数为20%硫酸m2g(硫酸 足量),充分反应、冷却后称量.根据溶液总质量m判断该氢氧化钠溶液是否变质.

试结合该方案,回答下列问题:

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