问题 填空题

已知某溶液中只存在OH-、H+、Cl-四种离子,某同学推测其离子浓度大小顺序有如下四种关系:

①c(Cl-)>c()>c(H+)>c(OH-)②c(Cl-)>c()>c(OH-)>c(H+

③c()>c(Cl-)>c(OH-)>c(H+)④c(Cl-)>c(H+)>c()>c(OH-

填写下列空白:

(1)若溶液中只溶解了一种溶质,则该溶液是_______________,上述四种离子的浓度的大小顺序为_______________(填序号)。

(2)若上述关系中③是正确的,则溶液中的溶质为_______________;若上述关系中④是正确的,则溶液中的溶质是_______________。

(3)若该溶液是由体积相等的稀盐酸和氨水混合而成,且恰好成中性,则混合前c(HCl)_________c(NH3·H2O)(填“大小”“小于”或“等于”)。

答案

(1)NH4Cl①(2)NH4Cl和NH3·H2ONH4Cl和HCl(3)小于

据题意四种离子两两结合可得NH4Cl、NH3·H2O、HCl三种溶质。

(1)若溶液只溶解一种溶质,只有NH4Cl作为溶质时,溶液中才同时存在以上四种离子。因存在微弱的水解反应+H2ONH3·H2O+H+,c()减小,c(H+)>c(OH-),故溶液中c(Cl-)>c()>c(H+)>c(OH-)。

(2)若溶液中存在c()>c(Cl-)>c(OH-)>c(H+),由c(OH-)>c(H+)可知溶液呈碱性,故溶液可由NH4Cl和NH3·H2O混合而得,即溶质为NH4Cl和NH3·H2O;若溶液中存在c(Cl-)>c(H+)>c()>c(OH-),由c(H+)>c()可知溶液的酸性大于纯NH4Cl溶液的酸性,故溶液可由NH4Cl和盐酸混合而得。

(3)若NH3·H2O和盐酸等体积混合后,溶液呈中性,则有c(H+)=c(OH-),c()=c(Cl-)n()=n(Cl-),因溶液中有未反应的NH3·H2O,则混合前n(NH3·H2O)>n(HCl)c(NH3·H2O)>c(HCl)。

阅读理解

Since the 1970s, scientists have been searching for ways to link the brain with computers.Brain-computer interface(BCI) technology could help people with disabilities send commands to machines.

Recently, two researchers, Jose Millan and Michele Tavella from the Federal Polytechnic School in Lausanne, Switzerland, demonstrated(展示)a small robotic wheelchair directed by a person’s thoughts.

In the laboratory, Tavella operated the wheelchair just by thinking about moving his left or right hand.He could even talk as he watched the vehicle and guided it with his thoughts.

“Our brain has billions of nerve cells.These send signals through the spinal cord(脊髓)to the muscles to give us the ability to move.But spinal cord injuries or other conditions can prevent these weak electrical signals from reaching the muscles,” Tavella says.“Our system allows disabled people to communicate with external world and also to control devices.”

The researchers designed a special cap for the user.This head cover picks up the signals from the scalp(头皮)and sends them to a computer.The computer interprets the signals and commands the motorized wheelchair. The wheelchair also has two cameras that identify objects in its path.They help the computer react to commands from the brain.

Prof.Millan, the team leader, says scientists keep improving the computer software that interprets brain signals and turns them into simple commands.“The practical possibilities that BCI technology offers to disabled people can be grouped in two categories: communication, and controlling devices.One example is this wheelchair.”

He says his team has set two goals.One is testing with real patients, so as to prove that this is a technology they can benefit from.And the other is to guarantee that they can use the technology over long periods of time.

小题1:BCI is a technology that can         .

A.help to update computer systems

B.link the human brain with computers

C.help the disabled to recover

D.control a person's thoughts小题2:How did Tavella operate the wheelchair in the laboratory?                                    

A.By controlling his muscles.

B.By talking to the machine.

C.By moving his hand.

D.By using his mind.小题3:The team will test with real patients to         .

A.make profits from them

B.prove the technology useful to them

C.make them live longer

D.learn about their physical condition小题4:Which of the following would be the best title for the text?

A.Switzerland, the BCI Research Center

B.New Findings About How the Human Brain Works

C.BCI Could Mean More Freedom for the Disabled

D.Robotic Vehicles Could Help to Cure Brain Injuries

单项选择题