问题
计算题
已知潜水员在岸上和海底吸入空气的密度分别为1.3kg/m3和2.1kg/m3，空气的摩尔质量为0.029kg/mol，阿伏伽德罗常数NA=6.02
。若潜水员呼吸一次吸入2L空气，试估算潜水员在海底比在岸上每呼吸一次多吸入空气的分子数。（结果保留一位有效数字）
答案
个
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已知潜水员在岸上和海底吸入空气的密度分别为1.3kg/m3和2.1kg/m3，空气的摩尔质量为0.029kg/mol，阿伏伽德罗常数NA=6.02。若潜水员呼吸一次吸入2L空气，试估算潜水员在海底比在岸上每呼吸一次多吸入空气的分子数。（结果保留一位有效数字）
个
| 根据句子意思，从方框中选择恰当的单词填空。 | |
2. —What do you often do after school? —We often _______ baseball. 3. —How many times have you been to Nanning? — _______. 4. My dream is to buy a big and _______ house for my grandparents. 5. My brother likes chemistry and he does _______ in it. 6. Mum, don't worry. We can look after _______. 7. —Summer holiday is coming. What are we going to do? —Why not _______ in the swimming pool near our school? 8. —Where's your brother? —He has _______ to work. He'll be back in an hour. 9. —Are your students _______ in geography? —Yes. Because it's very useful. 10. Mr. Wei is a funny man. He often makes us _______. |
