问题 问答题

用化学式填写

(1)密度最小的气体______

(2)干冰______

(3)能造成酸雨的一种气体______

(4)地壳中含量最多的金属元素与氧元素组成的化合物______

(5)石灰水中的主要成分是______

(6)农业生产中,硝酸铵是重要的氮肥之一,其化学式为______.

答案

(1)氢气是密度最小的气体,它的化学式为H2,故密度最小的气体是H2

(2)干冰是固态的二氧化碳,二氧化碳由显+4价的碳元素和显-2价的氧元素组成,根据化合价原则,其化学式为:CO2

(3)酸雨是由于空气中二氧化硫或二氧化氮气体与空所中水形成酸的结果;二氧化硫由显+4价的硫元素和显-2价的氧元素组成,根据化合价原则,其化学式为:SO2

(4)地壳中含量最多的前五种元素是:氧、硅、铝、铁、钙,所以地壳中含量最多的金属元素是铝,其在化合物中通常显+3价,氧元素显-2价,根据化合价原则,其化学式为:Al2O3

(5)石灰水中的主要成分是氢氧化钙,钙元素显+2价,氢氧根显-1价,根据化合价原则,其化学式为:Ca(OH)2

(6)硝酸铵由显+1价的铵根离子和显-1价的硝酸根离子组成,根据化合价原则,其化学式为:NH4NO3

故答案为:(1)H2;(2)CO2;(3)SO2;(4)Al2O3;(5)Ca(OH)2;(6)NH4NO3

完形填空
完形填空。
     It's seven in the morning. After  1 , Mr White and Mrs White take their  2  to the school  3  the car. Then
they go to work in a  4 . The children have lunch at school. Father and mother have lunch at the factory.
There  5  four classes in the morning and two in the afternoon. After  6 , the children stay in the library some
time. Sometimes they  7  games with their classmates. Then they go home by school bus. Mother cooks
supper for the  8 , The children help their mother do the housework.
     After supper, the children do  9  . Father and mother watch TV or  10 .
( )1. A. lunch         
( )2. A. children      
( )3. A. on           
( )4. A. hospital      
( )5. A. has           
( )6. A. classes       
( )7. A. clean         
( )8. A. home         
( )9. A. their homework
( )10. A. read book    
B. supper        
B. students       
B. by             
B. factory        
B. are            
B. school         
B. stay           
B. child          
B. their homeworks
B. do some reading
C. dinner           
C. classmates       
C. at               
C. school           
C. is              
C. lunch            
C. wash             
C. herself          
C. their housework  
C. make some reading
D. breakfast          
D. friends              
D. in                    
D. restaurant           
D. have                  
D. afternoon             
D. play                  
D. family                
D. his homework          
D. do some reading books 
单项选择题