已知下面三个数据：①7.2×10-4、②2.6×10-4、③4.9×10-10分别是三种酸的电离平衡常数，若已知这三种酸可发生如下反应：NaCN+HNO2==HCN+NaNO2；NaCN+HF="=HCN+NaF" ； NaNO2+HF==HNO2+NaF ；由此可判断下列叙述中正确的是
A．HF的电离常数是①
B．HNO2的电离常数是①
C．HCN的电离常数是②
D．HNO2的电离常数是③
答案：A
正确答案：A
由三个方程式得酸性强弱顺序为：HF >HNO2> HCN
A、正确，HF酸性最强，电离常数最大；B. HNO2的电离常数是②
C. HCN的电离常数是③ D. HNO2的电离常数是②
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Twice in the 20th century, the city was (3)______ and rebuilt (重建). In 1923, there was a great earthquake in the city. (4)______ of people were killed and millions left homeless. It (5)______ people there seven years to rebuild the city. During World War ?, Tokyo was destroyed once again. After the disasters (灾难), nothing (6)______ in the downtown area of old Tokyo. After the war, the people of Tokyo began to rebuild their city. The city was (7)______ at a high speed (高速地) between 1945 and 1960, and the city's population (8)______ very fast. As a result of this quick development, however, many problems have (9)______, such as housing shortage (短缺), pollution and unemployment (失业). But the government has (10)______ several programs to solve them. |