阿伏加德罗常数的值约为6.02×1023mol－1，下列叙述中正确的是
A．2mol SO2和1 mol O2混合在V2O5存在的条件下于密闭容器中加热反应后，容器内物质分子数等于2×6.02×1023
B．电解精炼铜时转移了6.02×1023个电子，阴极析出32 g铜
C．2.9g 2CaSO4·H2O含有的结晶水分子数为0.02×6.02×1023(2CaSO4·H2O式量为290)
D．含0.2 mol H2SO4的浓硫酸与足量铜反应，生成SO2的分子数为0.1×6.02×1023
答案：B
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| Peter and James were brothers. One afternoon __1__ the lessons were over, they stayed in school to help their teacher. They__ 2__ for an hour. Then the teacher said, "Thank you, boys. We will finish the work tomorrow. Now you must go home." When the boys __3__ home, it was seven o'clock. There was light inside their house and the door was ___4__. They could see a man inside, too. "Who can it be?" thought Peter. "Father and Mother have gone shopping. They won't be home __5__ eight o'clock." When the ___6__ man saw Peter, he smiled and said, "Come in! You don't know me, but I'm your __7__friend. He asked me to fetch (取)some money for him." The man did not see James. Peter went inside and began talking to the man but James did not. He quietly but quickly ran off to call the police. He soon found a policeman and __8__ him back to their home. The man was still there, but when he saw the policeman, he tried to run off. The policeman __9__ him and held his arm. Just then Mr. and Mrs. Baker, the boys' parents _10__. "No!" said Baker. "I don't know him. He must be a thief. I am glad you have caught him."
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