问题 实验题

高纯MnCO3是制备高性能磁性材料的主要原料。实验室以MnO2为原料制备少量高纯MnCO3的操作步骤如下:

(1)制备MnSO4溶液:在烧瓶中加入一定量MnO2和水,搅拌,通入SO2和N2混合气体,反应3h。停止通入SO2,继续反应片刻,过滤 (已知MnO2+H2SO3=MnSO4+H2O)。

①石灰乳参与反应的化学方程式为____________________

②反应过程中,为使SO2尽可能转化完全,在通入SO2和N2比例一定、不改变固液投料的条件下,可采取的合理措施有________________、____________________。

③若实验中将N2换成空气,测得反应液中Mn2+、SO42-的浓度随反应时间t变化如下图。导致溶液中

Mn2+、SO42-浓度变化产生明显差异的原因是____________________

(2)制备高纯MnCO3固体:已知MnCO3难溶于水、乙醇,潮湿时易被空气氧化,100℃开始分解;

Mn(OH)2开始沉淀时pH=7.7。请补充由(1)制得的MnSO4溶液制备高纯MnCO3的操作步骤[实验中可选用的试剂:Ca(OH)2、NaHCO3、Na2CO3、C2H5OH]

①________;②________;③________;④_______;⑤低于100℃干燥。

答案

(1)①Ca(OH)2+SO2=CaSO3+H2O;②控制适当的温度;缓慢通入混合气体;③Mn2+催化O2与H2SO3反应生成H2SO4

(2)①边搅拌边加入NaHCO3(Na2CO3),并控制溶液pH<7.7;②过滤,用少量水洗涤2~3次;③检验SO42-

是否被洗涤除去;④用少量C2H5OH洗涤

多项选择题
阅读理解

阅读理解。

     Speeding off in a stolen car, the thief thinks he has got a great catch. But he is in for an unwelcome surprise.

The car is fitted with a remote immobilizer (远程控制器) and a radio signal from a control center miles away

will make sure that once the thief turns the engine off, he will not be able to start it again.

     The idea goes like this. A control box fitted to the car contains a mini-cell phone, a micro-processor and

memory and a GPS satellite positioning receiver. If the car is stolen, a coded (编码的) cell phone signal will tell

the control center to block the vehicle's engine management system and prevent the engine being restarted.

     In the UK, a set of technical fixes is already making life harder for car thieves. "The pattern of vehicle crime

has changed," says Martyr Randall, a security expert. He says it would only take him a few minutes to teach a

person how to steal a car, using a minimum of tools, but only if the car is more than 10 years old.

     Modern cars are far tougher to steal, as their engine management computer won't allow them to start unless

they receive a unique ID code beamed out by the ignition (点火) key. In the UK, technologies like this have

helped to achieve a 31% drop in vehicle crime since 1997.

     But determined thieves are still managing to find other ways to steal cars, often by getting hold of the owner's

keys. And key theft is responsible for 40% of the thefts of vehicles fitted with a tracking system.

     If the car travels 100 meters without the driver conforming (一致) the ID, the system will send a signal to

an operation center that it has been stolen. The 100-meter minimum avoids false alarm be- cause of some

possible errors of the GPS signal.

     Staff at the center will then contact the owner to confirm that the car really is missing and keep the police

informed of the vehicle's movements via the car's GPS unit.

1. What's the function of the remote immobilizer fitted to the car? [ ]

A. To help the police make a surprise attack on the car thief.

B. To order the car to lock automatically when stolen.

C. To prevent the car thief from restarting it once it stops.

D. To send a radio signal to inform the car owner of the theft.

2. The underlined sentence "The pattern of vehicle crime has changed" suggests that ____. [ ]

A. it takes less time for the car thief to do the stealing

B. many self-prepared too]s can be used for car theft

C. the theft becomes more difficult because of modern technology

D. the thief has lost interest in stealing cars over 10 years old

3. ____ is essential in making a modern car tougher to steal.[ ]

A. A micro-processor

B. A special ID code

C. A special cell phone

D. A GPS satellite positioning receiver

4. Why does the tracking system set a 100-meter minimum before sending an alarm to the operation center? [ ]

A. To leave time for the operation center to give an alarm.

B. To keep the police informed of the car's movement.

C. To give the driver time to contact the operation center.

D. To allow for possible mistakes in the GPS system.

5. What will the operation center do first after receiving an alarm?[ ]

A. Start the tracking system.

B. Stop the engine.

C. Contact the owner.

D. Locate the missing car.