对于反应3Fe(s)＋4H2O(g)
Fe3O4(s)＋4H2(g)的平衡常数，下列说法正确的是
A．K＝
B．K＝
C．增大c(H2O)或减小c(H2)，会使该反应平衡常数减小
D．改变反应的温度，平衡常数不一定变化
答案：B
题目分析：化学平衡常数是在一定条件下，当可逆反应达到平衡状态时，生成物浓度的幂之积和反应物浓度的幂之积的比值，所以根据反应式3Fe(s)＋4H2O(g)
Fe3O4(s)＋4H2(g)可知，该反应的平衡常数K＝
，A不正确，B正确；C、平衡常数只与温度有关系，所以增大c(H2O)或减小c(H2)，该反应的平衡常数不变，C不正确；D、平衡常数只与温度有关系，所以改变反应的温度，平衡常数一定变化，D不正确，答案选B。
Alicia was a young woman who liked to exercise for her health. In fact, she walked five kilometers before every morning, and went swimming once a week at the swimming pool. She didn’t smoke and never . She didn’t eat chocolate. She didn’t eat sweet and fatty food, . She weighted herself every day. One day Alicia was on her daily walk when she saw a sitting in a rocking chair under a tree. He looked very old and his hair was white. He looked thin and weak, and his hands were shaking, he looked very happy. He smiled at her and said, “Good morning! Lovely day, isn’t it?” He had a wide smile his face, and his eyes shone with happiness. But Alicia saw that he did not have teeth. “Good morning!” replied Alicia. “Yes, it is a lovely day.” Alicia thought he very old and wise. She thought he must be at least 90 years old! She decided to ask him about the of a happy old age. “I hope you don’t me asking,” she said, “but what is your secret for being so happy at your age? I hope I can look as happy as you do I am your age.” The man in the rocking chair said, “My secret for ? I smoke twenty packets of cigarettes every week, and drink three bottles of wine every day. I eat hamburgers and chocolates whenever I want. I never eat vegetables. I never walk anywhere and I never play sports. I sit at home every day.” Alicia was . She didn’t expect the man to give her an answer like that. She wondered how the man got to be so old when he did wrong. She thought he should be and unhappy. Perhaps she was wrong. Maybe, she thought, people could live a long happy life eating well or doing lots of exercise. “How old are you?” she asked. “It’s my birthday today,” said the man. “I’m forty-seven!”
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