问题 选择题

已知:25°C时,KSP[Mg(OH)2]=5.61×10—12,KSP[MgF2]=7.42×10—11。下列说法正确的是(   )

A.25°C时,饱和Mg(OH)2溶液与饱和MgF2溶液相比,前者的c(Mg2+)大

B.25°C时,在Mg(OH)2的悬浊液加入少量的NH4Cl固体,c(Mg2+)增大

C.25°C时,Mg(OH)2固体在20ml0.01mol/L氨水中的KSP比在20mL0.01mol/LNH4Cl溶液中的KSP

D.25°C时,在Mg(OH)2的悬浊液加入NaF溶液后,Mg(OH)2不可能转化成为MgF2

答案

答案:B

氢氧化镁的溶度积常数小于氟化镁的,所以A不正确。由于氯化铵溶于水,电离出NH4能结合溶液中OH,促进氢氧化镁的溶解,B正确。溶度积常数只与温度有关系,C不正确。只要溶液中c(Mg2)·c2(OH)>KSP[MgF2],就会有氟化镁沉淀析出,D不正确。答案选B。

阅读理解

Bruno was a boy of eight. His father worked in a cinema and his mother worked in a shop. He lived not far from his school. He always walked there and walked home. On his way to school, he had to pass a playground. It was very wet after it rained. One day, when he got home, his clothes were all wet. His mother became angry(生气的)and said, “Don’t play in the water on your way home from school!”

On the next day Bruno came home with wet and dirty(脏的)clothes. His mother became even angrier. “I’ll tell your father if you come back wet again,” said his mother. “He’ll punish(惩罚)You, you know.”

The third day the little boy was dry when he came home.

“You’re a good boy today”, his mother said happily. “You didn’t play in the water.”

“No,” the boy said unhappily. “There were too many older boys in the water when I got there this afternoon. There wasn’t any room(空地方)for me at all!”

根据文章内容选择正确答案

小题1:Bruno went to school     every day.

A.by bike

B.by bus

C.by car

D.on foot小题2:The playground was between(在……之间)                    

A.two classrooms

B.the cinema and shop

C.Bruno’s house and school

D.the shop and Bruno’s school小题3:The little boy liked to play on the playground                    .

A.when it snowed

B.when there was some water there

C.when the children played football there

D.when his father was busy with his work小题4:54.Bruno was afraid of         the most.

A.his father

B.his mother

C.his teacher

D.the older boys小题5:That afternoon, the boy’s clothes were dry because         .

A.nobody made room(地方)for him in the water

B.there was no water on the playground

C.he took off his clothes before he played there

D.he played in the water carefully

不定项选择