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问题 选择题

将51.2gCu完全溶于适量浓硝酸中，收集到氮的氧化物（含NO、N2O4，NO2）的混合物共0.8mol，这些气体恰好能被500mL 2mol/L NaOH溶液完全吸收，发生的反应为：2NO2+2NaOH=NaNO2+NaNO3+H2O，NO+NO2+2NaOH=2NaNO2+H2O则生成的盐溶液中NaNO3的物质的量为（　　）

A．0.4mol

B．0.2mol

C．0.6mol

D．0.8mol

答案

51.2gCu的物质的量为

51.2g
64g/mol
=0.8mol，

铜和硝酸反应铜还原硝酸生成氮氧化合物，在NaOH溶液中氮氧化合物又转化成NaNO3和NaNO2，

则铜将失去的电子给了硝酸在氢氧化钠溶液中生成了NaNO2，

根据得失电子数目相等得到2n（Cu）=2n（NaNO2），

所以n（NaNO2）=n（Cu）=0.8mol，

根据钠元素守恒可知n（NaNO2）+n（NaNO3）=0.5L×2mol/L=1mol．

所以n（NaNO3）=1mol-0.8mol=0.2mol．

故选B．

单项选择题

The Erie Canal was the first important national waterway built in the US. It crossed New York from Buffalo on Lake Erie Troy to Albany on the Hudson River. It joined the Great Lakes with the Atlantic Ocean. The canal served as a route over which industrial goods could flow into the west, and materials could pour into the east. The Erie Canal helped New York develop into the nation’s largest city.

The building of the canal was paid for entirely by the state of New York. It cost $ 7 143 789, but it soon gained its price many times over. Between 1825, when the canal was opened, and 1882, when toll charges were stopped, the state collected $121461891.

For a hundred years before the Erie was built, people had been talking about a canal which could join the Great Lakes and the Atlantic Ocean. The man who planned the Erie Canal and carried the plan through was De Witt Clinton. Those who were against the canal laughingly called it "Clinton’s Ditch". Clinton talked and wrote about the canal and drew up plans for it. He and Governor Morris went to Washington in 1812 to ask for help for the canal, but they were unsuccessful.

Clinton became governor of New York in 1817, and shortly afterwards, on July 4, 1817, broke ground for the canal in Rome, N.Y. The first part of the canal was completed in 1820. As the canal grew, towns along its course developed fast. The length of the canal is 363 miles.

It can be inferred that（）into the Atlantic Ocean.

A. the Great Lakes flow

B. the Hudson River flows

C. Lake Erie flows

D. the Erie Canal flows
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填空题

水泵的扬程的大小与叶轮（）、叶轮数量的多少以及水泵的转速高低有关。
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