问题 填空题

如图为一定量饱和Ca(OH)2溶液中通入二氧化碳气体后,产生CaCO3白色沉淀的质量与二氧化碳体积之间的关系曲线.试回答:

OA段曲线和AB段曲线所表示的反应方程式是:

OA段______;AB段______;OA段=AB段原因是______

B处溶液中存在的浓度较大的两种离子是______和______(填离子符号)

将B处生成的溶液煮沸,可见到的现象是______.

答案

OA段:在Ca(OH)2溶液中通入二氧化碳气体,先生成CaCO3(不溶于水),反应的离子方程式为:Ca(OH)2+CO2=CaCO3↓+H2O;

AB段:当碱消耗完,再通入二氧化碳,二氧化碳与碳酸钙、水继续反应生成Ca(HCO32(溶于水),反应离子方程式为:Ca(HCO32=CaCO3↓+CO2↑+H2O;

根据反应的离子方程式可知,生成CaCO3沉淀和CaCO3沉淀溶解所消耗的二氧化碳的量相等,所以OA段=AB段;

B处氢氧化钙与二氧化碳恰好完全反应生成了碳酸氢钙,浓度较大的两种离子为:Ca2+;HCO3-

将B处生成的溶液煮沸,由于碳酸氢钙不稳定,加热时易分解,又转化为碳酸钙,

故答案为:Ca(OH)2+CO2=CaCO3↓+H2O;Ca(HCO32=CaCO3↓+CO2↑+H2O;生成CaCO3沉淀和CaCO3沉淀溶解所消耗的二氧化碳的量相等;

Ca2+;HCO3-;有白色沉淀生成.

阅读理解

The journey two naval (海军) officers made some time ago to tile very deepest point on the earth makes us realize how much of the world still remains to be explored (探测). The two men went down several miles to the bottom of the Pacific Ocean hiding in a small steel ball called a “bathy-scaphe” to find out if there are any ocean currents (急流) or signs of life.

It was necessary to set ont early, so that the bathyscaphe would come to the surfacc in daylight, and so be easily found by the mother ship which would be waiting for it. The divers began preparations at dawn and soon afterwards, when all was ready, the steel ball disappeared under the surface of the water.

In time, the temperature dropped to freezing-point and the men trembled inside the ball. They kept in touch with the mother ship by telephone describing how they felt. Then, at a depth of 3 000 feet, the telephone stopped working and they were quite cut off from the outside world. At 30 000 feet, the men were surprised by a sudden, loud noise-------even the smallest hole in the ball would have meant instant death. Luckily, though, it was only one of the outer windows that had broken. Soon afterwards, the bathyscaphe touched the soft ocean floor, raising a big cloud of “dust” made up of different kinds of small, dead sea animals. Here, powerful lights lit up the dark water and the men were surprised to see fish swimming just above them quite untroubled by thc very large wate-pressure. But they did not dare to leave the lights on for long, as the heat from them made the water boil. Quite unexpectedly, the telephone began working again and the weak but clear voices of the officers were heard on thc mother ship. After a stay of thirty minutes the men began their journey up, arriving three hours later, cold and wet through, but none the worse for their experience.

小题1:The officers started their journey at dawn___.  

A.because they wanted to return to the mother ship in twenty four hours

B.because the sea then was calm

C.when the sun was not too strong

D.so that they could return before dark小题2:What did the officers find out at the bottom of the sea?  

A.They only found different dead sea animals.

B.They did find signs of life.

C.There was no signs of any life.

D.There was only dust.小题3:The journey to the bottom of the sea helped us to realize that______. 

A.much of the world hasn’t yet been explored

B.there are not any signs of life at the bottom of the sea

C.strong water-pressure has great effect on fish

D.powerful lights can not be turned on at the ocean floor without killing fish小题4:Which of the following is closest in meaning to “They were cold and wet through, but none the worse for their experience”?   

A.They were cold and wet through, which was the worst thing of all.

B.They were even worse than cold and wet through at the bottom of the sea.

C.Considering what they had just experienced, being cold and wet through was not too

bad.

D.For such an experience, being cold and wet through was not bad for them at all.

单项选择题