问题 选择题

如果1g水中有m个氢原子,则阿伏加德罗常数为(  )

A.

m
9

B.9m

C.2m

D.

m
2

答案

阿伏伽德罗常数用NA表示,1g水的物质的量=

1g
18g/mol
=
1
18
mol
,含氢原子物质的量=
1
9
mol
,m个氢原子物质的量=
m
NAmol-1
=
m
NA
mol
,依据氢原子物质的量相同得到
1
9
=
m
NA
,得到NA=9m;

故选B.

单项选择题
阅读理解

阅读理解。

     Su Hua is studying at Cambridge, UK. She has bought a bicycle and is worried about security. Her

friend, Kate, found this article and sent it to her.

     Introduction

     A lot of crime is against bicycles. About 150,000 bicycles are stolen every year and most are never

found. You can prevent this happening by following a few careful steps.

     Basic Security

     Do not leave your bicycle in out-of-the-way places. Always lock your bicycle when you leave.

Secure it to lampposts or trees. Take off smaller parts and take them with you, for example lights and

saddles(车座).

     Locks

     Get a good lock. There are many different types in the shop. Buy one that has been tested against

attack. Ask for a recommendation from a bike shop.

     Marking

     Security marking your bike can act as a deterrent to a thief. It can also help the police find your

bicycle. It should be clearly written and include your postcode and your house or flat number. This will

provide a simple way to identify your bicycle.

     Registration

     There are a number of companies who will security mark your bicycle for you. They will then put

your registration number and personal details on their computer database. Then if your bicycle is found

it will be easy to contact you.

     Finally

      Keep a record of the bicycle yourself: its make, model and registration number. You can even take

a photograph of it, this will prove the bicycle belongs to you.

1. Which part of the article gives you information on how to lock up your bicycle when you leave it?

A. Locks      

B. Marking      

C. Registration      

D. Basic Security

2. The underlined phrase "act as a deterrent to a thief" means__________ .

A. help you recognize your bike          

B. help the police find your bicycle

C. stop someone stealing your bicycle      

D. stop you worrying about your bike

3. The article advises you to keep a record of your bicycle ____________. 

A. in the bike shop and your computer

B. in a police station and security company

C. in a security company and your university

D. by yourself and in a security company

4. The main purpose of this article is _____________. 

A. to tell you what to do if your bicycle is stolen

B. to suggest ways of keeping your bicycle safe

C. to give you advice on where to buy a good lock

D. to say why you shouldn't keep your bicycle in a quiet place