（6分）现有20g大理石(杂质不参加反应)，与100克稀盐酸恰好完全_爱下问搜题

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问题计算题

（6分）现有20g大理石(杂质不参加反应)，与100克稀盐酸恰好完全反应，反应后烧杯中剩余物质的总质量为115.6克。计算:

(1)生成的二氧化碳_________g。

(2)求大理石中碳酸钙的质量分数。

答案

（1）4.4g (2) 50%

题目分析：（1）根据质量守恒定律，化学反应前后物质的总质量不变，所以生成的二氧化碳的质量为20g+100g-115.6g=4.4g

（2）设大理石中碳酸钙的质量为x

CaCO₃ + 2HCl =" CaCl" ₂+ CO₂↑ + H₂O

100 44

x 4.4g

x =

x =10g

大理石中碳酸钙的质量分数为 10g/20gX100%=50%

点评：根据化学方程式的计算除了理解化学方程式的意义，会根据化学方程式进行计算外，还应注意化学方程式的书写要正确，计算格式要规范。

完形填空

Two men, both seriously ill, were in the same hospital room. One man was allowed to 46 in his bed for an hour each afternoon for treatment. His 47 was next to the room's only window. The other man 48 spend all his time flat on his back. Every 49 when the man in the bed by the window could sit up, he 50 pass the time by describing(描述) to his 51 all the things he could see outside the window. The window overlooked（远眺） a 52 with a lovely lake. Ducks played on the water while children 53 their model boats. Young lovers walked 54 among flowers. As the man by the window described all this beautifully, the other man would close his eyes and 55 the scene.
One morning, the day nurse arrived to bring water for their baths only to find the 56 body of the man by the window, who had died 57 in his sleep. She was sad and 58 the hospital attendants (服务员) to take the body away. 59 it seemed appropriate (合适的), the other man asked if he could 60 next to the window. The nurse was happy to make the switch（调换）, and after 61 he was comfortable, she left him alone. Slowly and painfully, he sat up to take his 62 look at the world outside. Finally, he would have the 63 of seeing it for himself. He strained (紧张地) to slowly turn to 64 the window beside the bed. It faced a blank wall.
The man asked the nurse what could have forced his dead roommate to 65 those wonderful things outside this window. The nurse answered that the man was blind and could not even see the wall. She said, “Perhaps he just wanted to encourage you.”

B．would rather

D．rather than

A．face to face

B．shoulder to shoulder

D．back to back

A．making sure

B．depending on

D．accounting for

填空题

气体在压缩机内压缩，排气压力（），排气温度将降低。