问题 选择题

某混合气体,经分析只含碳、氧两种元素,且氧元素与碳元素的质量比大于8:3.则混合气体的组成不可能是(  )

A.CO2和O2

B.CO和O2

C.CO和CO2

D.CO、CO2和O2

答案

二氧化碳气体中氧、碳元素的质量比=(16×2):12=8:3;一氧化碳气体中氧、碳元素质量比=16:12=4:3;假设气体全部为二氧化碳,气体中氧、碳元素质量比也只能达到8:3,全部为一氧化碳中氧、碳元素的质量比为4:3,而混合气体中氧、碳质量比大于8:3,故结合题给选项可以作出如下判断:

A、二氧化碳中氧、碳元素的质量比为:8:3,若混有了氧气,则其中氧、碳元素的质量比可能大于8:3;故A可能;

B、一氧化碳中氧、碳元素的质量比为4:3,所以若混有了氧气,则其中氧、碳元素的质量比可能大于8:3,故B可能;

C、若混和气体为CO、CO2,则由于二氧化碳中氧、碳元素的质量比为:8:3,一氧化碳中氧、碳元素的质量比为4:3,所以两种气体混合后的质量比不可能大于为8:3,故不C可能;

D、二氧化碳中氧、碳元素的质量比为:8:3,一氧化碳中氧、碳元素的质量比为4:3,所以若混有了氧气,则其中氧碳元素的质量比可能大于8:3,故D可能.

故选C.

完形填空
Zigfried, a little mouse, blew his breath on the frosty window of the farmhouse and rubbed it to see the outside. Still nobody came. Maybe today, he thought  31 . It was only a few days before Christmas and he was watching for a miracle (奇迹).
This farmhouse had been  32  too long. It needed a family. Zigfried’s  33  made a noise. He realized that he hadn’t eaten anything since yesterday. He jumped from the windowsill (窗沿), grabbed a  34  from his home, and went next door to Farmer Mike’s.
Farmer Mike’s house had been a great place for the little mouse  35  the farmer married a wife who had a cat. Zigfried  36  when he thought of it. He looked around cautiously as he 37  into the room where grain was stored and was quite  38  as he filled his bag with wheat. He was turning to leave when suddenly he  39  a hot breath about his ear. His heart beat  40  , and without thinking he started to run and luckily  41  the cat’s paws (爪子).
The next afternoon Zigfried heard some good news: a  42  family would be moving into the farmhouse soon. Zigfried’s granny would arrive on Christmas Eve to  43 with him. He hoped that the family would come before his granny came. Before long, a car came  44  the road leading to the house, with butter sandwiches, cheese and chocolate.
Zigfried’s Christmas miracle did arrive!
The house came  45  the next few days. Zigfried  46  every single hour of them.  47 , the day before Christmas when he was drinking hot chocolate with a  48  smile at the door of his home, he heard the  49 of the children of the family about what they might get for Christmas. What? A cat? The  50  froze on his face; his mouth fell wide open. After a long while, he at last found his voice: “Hey! Whose Christmas miracle is this?”
小题1:
A.carefully B.excitedly C.hopefully D.proudly
小题2:
A.shabby B.noisy C.messyD.empty
小题3:
A.mouth B.nose C.stomach D.throat
小题4:
A.bag B.stick C.bowl D.coat
小题5:
A.although B.until C.whereas D.unless
小题6:
A.leapt B.sniffedC.trembledD.withdrew
小题7:
A.broke B.marched C.paced D.stole
小题8:
A.curious B.nervous C.pitiful D.sensible
小题9:
A.took B.released C.felt D.drew
小题10:
A.strongly B.irregularly C.slowly D.wildly
小题11:
A.escaped B.seized C.rubbed D.scratched
小题12:
A.close B.happy C.new D.young
小题13:
A.celebrate B.communicateC.competeD.compromise
小题14:
A.across B.from C.off D.up
小题15:
A.alive B.loose C.open D.still
小题16:
A.counted B.enjoyed C.missed D.wasted
小题17:
A.However B.Instead C.Moreover D.Therefore
小题18:
A.bitter B.forced C.polite D.satisfied
小题19:
A.introductionB.discussion C.comment D.debate
小题20:
A.blood B.smile C.tear D.sweat
判断题