问题 填空题

从Fe、H2O、CO2、H2SO4、NaOH、CuCl2等物质中,选出适当的物质,按下列要求书写化学方程式:

(1)生成物使紫色石蕊溶液变成红色的化合反应______.

(2)有化合价变化的分解反应______.

(3)复分解反应______.

(4)有气体产生的置换反应______.

答案

(1)二氧化碳与水反应生成碳酸,碳酸能使紫色石蕊溶液变红色,所提供的物质中包含二氧化碳和水.

该反应的化学方程式为:CO2+H2O=H2CO3

(2)水在通电条件下反应生成氢气和氧气.

该反应属于分解反应;生成物中有单质,该反应过程中化合价有变化;所提供的物质中包含水.

该反应的化学方程式为:2H2O

 通电 
.
 
2H2↑+O2↑.

(3)稀硫酸与氢氧化钠反应生成硫酸钠和水,该反应属于酸与碱之间发生的复分解反应.所提供的物质中有硫酸和氢氧化钠.

该反应的化学方程式为:H2SO4+2NaOH=Na2SO4+2H2O.

(4)铁与稀硫酸反应生成硫酸亚铁和氢气.该反应属于置换反应,反应生成的单质是氢气.所提供的物质中有铁和硫酸.

该反应的化学方程式为:Fe+H2SO4=FeSO4+H2↑.

故答案为:

(1)CO2+H2O=H2CO3

(2)2H2O

 通电 
.
 
2H2↑+O2↑;

(3)H2SO4+2NaOH=Na2SO4+2H2O;

(4)Fe+H2SO4=FeSO4+H2↑.

单项选择题
单项选择题

Lying in the sun on a rock, the cougar(美洲狮) saw Jeb and his son, Tom, before they saw it. Jeb put his bag down quickly and pulled his jacket open with both hands, making himself look big to the cougar. It worked. The cougar hesitated, ready to attack Jeb, but ready to forget the whole thing, too.

Jeb took off his jacket, grasped Tom and held him across his body, making a cross. Now the cougar’ s enemy looked even bigger, and it rose up, ready to move away, but unfortunately Tom got scared and struggled free of Jeb.

"Tom, No !" shouted his father.

But Tom broke and ran and that’ s the last thing you do with a cougar. The second Tom broke free, Jeb threw himself on the cougar, just as it jumped from the rock. They hit each other in mid-air and both fell. The cougar was on Jeb in a flash, forgetting about Tom, which was what Jeb wanted. Cougars are not as big as most people think and a determined man stands a chance, even with just his fists. As the cougar’s claws got into his left shoulder, Jeb swung his fist at its eyes and hit hard. The animal howled(吼叫)and put its head back. Jeb followed up with his other fist. Then out of the comer of his eye, Jeb saw Tom. The boy was running back to help his father.

"Knife, Tom," shouted Jeb.

The boy ran to his father’ s bag, while Jeb started shouting as well as hitting, to keep the cou-gar’s attention away from Tom. Tom got the knife and ran over to Jeb. The cougar was moving its head in and out, trying to find a way through the wall. Jeb was making out of his arms. Tom swung with the knife, into the cougar’ s back. It howled horribly and ran off into the mountains.

What do we know about cougars()

A. They are afraid of noises.

B. They hesitate before they hit.

C. They are bigger than we think.

D. They like to attack running people.