题目

Recently, a study was carried out to determine who was the greatest American president．Sixty-five presidential historians took part in it, and they judged the past forty-two American leaders based on ten leadership qualities, including public persuasiveness(信服), crisis leadership, management of the economy, moral leadership, and conduct of international relations．The historians also looked at administrative ability (管理能力), relations with Congress, ability to set goals, and the pursuit of equal justice for all．Finally, the experts took into consideration the historical p生产硫酸最古老的方法是以绿矾为原料，在蒸馏釜中煅烧。反应的化学方程式为：2FeSO4·7H2O  Fe2O3 + SO2↑+ SO3↑+ 14H2O。其中三氧化硫与水蒸气同时冷凝便得到硫酸。用如图装置模拟用绿矾制硫酸的实验，并检验生成的硫酸和二氧化硫（加热装置已略去）。其中b为干燥的试管。下列关于该反应说法正确的是 A．若将反应后的三种气体通入BaCl2溶液中，产生的沉淀为BaSO3、BaSO4 B．b中产物用紫色石蕊试液即可检验出其中H+和SO42— C．为检验反应的另一种生成物，试管c中应加入的试剂为NaOH溶液 D．b中所得到的硫酸的质量分数为29.5%